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…ero control edit descriptors LZ, LZS, and LZP for formatted output (F, E, D, and G editing): LZ: processor-dependent (default, flang prints leading zero); LZS: suppress the optional leading zero before the decimal point; LZP: print the optional leading zero before the decimal point. Changes span the source parser, compile-time format validator, runtime format processing, and runtime output formatting. Includes semantic test (io16.f90) and documentation updates.
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@llvm/pr-subscribers-flang-semantics Author: None (laoshd) Changes…control edit descriptors LZ, LZS, and LZP for formatted output (F, E, D, and G editing): LZ: processor-dependent (default, flang prints leading zero); LZS: suppress the optional leading zero before the decimal point; LZP: print the optional leading zero before the decimal point. Changes span the source parser, compile-time format validator, runtime format processing, and runtime output formatting. Includes semantic test (io16.f90) and documentation updates. Full diff: https://github.com/llvm/llvm-project/pull/183500.diff 10 Files Affected:
diff --git a/flang-rt/include/flang-rt/runtime/format-implementation.h b/flang-rt/include/flang-rt/runtime/format-implementation.h
index d510adbb5ba46..8b341def2b3ce 100644
--- a/flang-rt/include/flang-rt/runtime/format-implementation.h
+++ b/flang-rt/include/flang-rt/runtime/format-implementation.h
@@ -193,7 +193,7 @@ static RT_API_ATTRS bool AbsoluteTabbing(CONTEXT &context, int n) {
template <typename CONTEXT>
static RT_API_ATTRS void HandleControl(
- CONTEXT &context, char ch, char next, int n) {
+ CONTEXT &context, char ch, char next, int n, char next2 = '\0') {
MutableModes &modes{context.mutableModes()};
switch (ch) {
case 'B':
@@ -251,6 +251,21 @@ static RT_API_ATTRS void HandleControl(
return;
}
break;
+ case 'L':
+ if (next == 'Z') {
+ if (next2 == 'S') {
+ // LZS - suppress leading zeros
+ modes.leadingZero = MutableModes::LeadingZeroMode::Suppress;
+ } else if (next2 == 'P') {
+ // LZP - print leading zero
+ modes.leadingZero = MutableModes::LeadingZeroMode::Print;
+ } else {
+ // LZ - processor-dependent (default behavior)
+ modes.leadingZero = MutableModes::LeadingZeroMode::Processor;
+ }
+ return;
+ }
+ break;
case 'S':
if (next == 'P') {
modes.editingFlags |= signPlus;
@@ -455,6 +470,7 @@ RT_API_ATTRS int FormatControl<CONTEXT>::CueUpNextDataEdit(
} else if (ch >= 'A' && ch <= 'Z') {
int start{offset_ - 1};
CharType next{'\0'};
+ CharType next2{'\0'};
if (ch != 'P') { // 1PE5.2 - comma not required (C1302)
CharType peek{Capitalize(PeekNext())};
if (peek >= 'A' && peek <= 'Z') {
@@ -464,6 +480,15 @@ RT_API_ATTRS int FormatControl<CONTEXT>::CueUpNextDataEdit(
// Assume a two-letter edit descriptor
next = peek;
++offset_;
+ } else if (ch == 'L' && peek == 'Z') {
+ // LZ, LZS, or LZP control edit descriptor
+ next = peek;
+ ++offset_;
+ CharType peek2{Capitalize(PeekNext())};
+ if (peek2 == 'S' || peek2 == 'P') {
+ next2 = peek2;
+ ++offset_;
+ }
} else {
// extension: assume a comma between 'ch' and 'peek'
}
@@ -484,7 +509,7 @@ RT_API_ATTRS int FormatControl<CONTEXT>::CueUpNextDataEdit(
repeat = GetIntField(context);
}
HandleControl(context, static_cast<char>(ch), static_cast<char>(next),
- repeat ? *repeat : 1);
+ repeat ? *repeat : 1, static_cast<char>(next2));
}
} else if (ch == '/') {
context.AdvanceRecord(repeat && *repeat > 0 ? *repeat : 1);
diff --git a/flang-rt/include/flang-rt/runtime/format.h b/flang-rt/include/flang-rt/runtime/format.h
index 79a7dd713b1a1..787772935ce8c 100644
--- a/flang-rt/include/flang-rt/runtime/format.h
+++ b/flang-rt/include/flang-rt/runtime/format.h
@@ -44,6 +44,12 @@ struct MutableModes {
return editingFlags & decimalComma ? char32_t{','} : char32_t{'.'};
}
+ enum class LeadingZeroMode : std::uint8_t {
+ Processor, // LZ: processor-dependent (default)
+ Suppress, // LZS: suppress optional leading zero
+ Print, // LZP: print optional leading zero
+ };
+
std::uint8_t editingFlags{0}; // BN, DP, SS
enum decimal::FortranRounding round{
executionEnvironment
@@ -53,6 +59,7 @@ struct MutableModes {
short scale{0}; // kP
bool inNamelist{false}; // skip ! comments
bool nonAdvancing{false}; // ADVANCE='NO', or $ or \ in FORMAT
+ LeadingZeroMode leadingZero{LeadingZeroMode::Processor}; // LZ/LZS/LZP
};
// A single edit descriptor extracted from a FORMAT
diff --git a/flang-rt/lib/runtime/edit-output.cpp b/flang-rt/lib/runtime/edit-output.cpp
index 73dba35ff08d9..d0aa8638102a9 100644
--- a/flang-rt/lib/runtime/edit-output.cpp
+++ b/flang-rt/lib/runtime/edit-output.cpp
@@ -411,10 +411,26 @@ RT_API_ATTRS bool RealOutputEditing<KIND>::EditEorDOutput(
if (totalLength > width || !exponent) {
return EmitRepeated(io_, '*', width);
}
- if (totalLength < width && digitsBeforePoint == 0 &&
- zeroesBeforePoint == 0) {
- zeroesBeforePoint = 1;
- ++totalLength;
+ if (digitsBeforePoint == 0 && zeroesBeforePoint == 0 && scale <= 0) {
+ // Optional leading zero position (F202X leading zero control).
+ // When scale > 0 (kP with k > 0), digits are moved before the decimal
+ // point, so the leading zero position is not optional -- skip this.
+ // Value has no digits before the decimal point: "0.xxxE+yy" vs ".xxxE+yy"
+ switch (edit.modes.leadingZero) {
+ case MutableModes::LeadingZeroMode::Print:
+ // LZP: always print the optional leading zero
+ zeroesBeforePoint = 1;
+ ++totalLength;
+ break;
+ case MutableModes::LeadingZeroMode::Suppress:
+ // LZS: never print the optional leading zero
+ break;
+ case MutableModes::LeadingZeroMode::Processor:
+ // LZ: processor-defined; flang chooses to print it
+ zeroesBeforePoint = 1;
+ ++totalLength;
+ break;
+ }
}
if (totalLength < width && editWidth == 0) {
width = totalLength;
@@ -544,7 +560,24 @@ RT_API_ATTRS bool RealOutputEditing<KIND>::EditFOutput(const DataEdit &edit) {
if (digitsBeforePoint + zeroesBeforePoint + zeroesAfterPoint +
digitsAfterPoint + trailingZeroes ==
0) {
- zeroesBeforePoint = 1; // "." -> "0."
+ zeroesBeforePoint = 1; // "."--> "0." (bare decimal point)
+ } else if (digitsBeforePoint == 0 && zeroesBeforePoint == 0 &&
+ expo <= 0) {
+ // Optional leading zero position (F202X leading zero control).
+ // Value magnitude < 1: "0.xxx" vs ".xxx"
+ switch (edit.modes.leadingZero) {
+ case MutableModes::LeadingZeroMode::Print:
+ // LZP: always print the optional leading zero
+ zeroesBeforePoint = 1;
+ break;
+ case MutableModes::LeadingZeroMode::Suppress:
+ // LZS: never print the optional leading zero
+ break;
+ case MutableModes::LeadingZeroMode::Processor:
+ // LZ: processor-defined; flang chooses to print it
+ zeroesBeforePoint = 1;
+ break;
+ }
}
int totalLength{signLength + digitsBeforePoint + zeroesBeforePoint +
1 /*'.'*/ + zeroesAfterPoint + digitsAfterPoint + trailingZeroes +
@@ -553,10 +586,6 @@ RT_API_ATTRS bool RealOutputEditing<KIND>::EditFOutput(const DataEdit &edit) {
if (totalLength > width) {
return EmitRepeated(io_, '*', width);
}
- if (totalLength < width && digitsBeforePoint + zeroesBeforePoint == 0) {
- zeroesBeforePoint = 1;
- ++totalLength;
- }
return EmitPrefix(edit, totalLength, width) &&
EmitAscii(io_, convertedStr, signLength + digitsBeforePoint) &&
EmitRepeated(io_, '0', zeroesBeforePoint) &&
diff --git a/flang/docs/F202X.md b/flang/docs/F202X.md
index d1940a1858db1..6a303981cf264 100644
--- a/flang/docs/F202X.md
+++ b/flang/docs/F202X.md
@@ -261,6 +261,15 @@ The `AT` edit descriptor automatically trims character output. The `LZP`,
`LZS`, and `LZ` control edit descriptors and `LEADING_ZERO=` specifier provide a
means for controlling the output of leading zero digits.
+Implementation status:
+- `LZ`, `LZS`, `LZP` control edit descriptors, affect only F, E, D, and G
+ editing of an output statement: Implemented
+ - `LZ` - Processor-dependent, default (e.g., `0.2`)
+ - `LZS` - Suppress leading zeros (e.g., `.2`)
+ - `LZP` - Print leading zero (e.g. `0.2`)
+- `AT` edit descriptor: Not yet implemented
+- `LEADING_ZERO=specifier` in OPEN statement: Not yet implemented
+
#### Intrinsic Module Extensions
Addressing some issues and omissions in intrinsic modules:
diff --git a/flang/docs/FortranStandardsSupport.md b/flang/docs/FortranStandardsSupport.md
index f57956cd6d6b8..02e4653280f12 100644
--- a/flang/docs/FortranStandardsSupport.md
+++ b/flang/docs/FortranStandardsSupport.md
@@ -48,7 +48,7 @@ status of all important Fortran 2023 features. The table entries are based on th
| Extensions for c_f_pointer intrinsic | Y | |
| Procedures for converting between fortran and c strings | N | |
| The at edit descriptor | N | |
-| Control over leading zeros in output of real values | N | |
+| Control over leading zeros in output of real values | P | LZ/LZS/LZP edit descriptors implemented; LEADING_ZERO=specifier not yet implemented |
| Extensions for Namelist | N | |
| Allow an object of a type with a coarray ultimate component to be an array or allocatable | N | |
| Put with Notify | N | |
diff --git a/flang/include/flang/Common/format.h b/flang/include/flang/Common/format.h
index 1e64acb823616..60bcc8e81ee38 100644
--- a/flang/include/flang/Common/format.h
+++ b/flang/include/flang/Common/format.h
@@ -114,7 +114,7 @@ struct FormatMessage {
// This declaration is logically private to class FormatValidator.
// It is placed here to work around a clang compilation problem.
ENUM_CLASS(TokenKind, None, A, B, BN, BZ, D, DC, DP, DT, E, EN, ES, EX, F, G, I,
- L, O, P, RC, RD, RN, RP, RU, RZ, S, SP, SS, T, TL, TR, X, Z, Colon, Slash,
+ L, LZ, LZP, LZS, O, P, RC, RD, RN, RP, RU, RZ, S, SP, SS, T, TL, TR, X, Z, Colon, Slash,
Backslash, // nonstandard: inhibit newline on output
Dollar, // nonstandard: inhibit newline on output on terminals
Star, LParen, RParen, Comma, Point, Sign,
@@ -219,7 +219,7 @@ template <typename CHAR = char> class FormatValidator {
std::int64_t knrValue_{-1}; // -1 ==> not present
std::int64_t scaleFactorValue_{}; // signed k in kP
std::int64_t wValue_{-1};
- char argString_[3]{}; // 1-2 character msg arg; usually edit descriptor name
+ char argString_[4]{}; // 1-3 character msg arg; usually edit descriptor name
bool formatHasErrors_{false};
bool unterminatedFormatError_{false};
bool suppressMessageCascade_{false};
@@ -390,7 +390,25 @@ template <typename CHAR> void FormatValidator<CHAR>::NextToken() {
token_.set_kind(TokenKind::I);
break;
case 'L':
- token_.set_kind(TokenKind::L);
+ switch (LookAheadChar()) {
+ case 'Z':
+ // Advance past 'Z', then look ahead for 'S' or 'P'
+ Advance(TokenKind::LZ);
+ switch (LookAheadChar()) {
+ case 'S':
+ Advance(TokenKind::LZS);
+ break;
+ case 'P':
+ Advance(TokenKind::LZP);
+ break;
+ default:
+ break;
+ }
+ break;
+ default:
+ token_.set_kind(TokenKind::L);
+ break;
+ }
break;
case 'O':
token_.set_kind(TokenKind::O);
@@ -674,9 +692,22 @@ template <typename CHAR> bool FormatValidator<CHAR>::Check() {
ReportError("Unexpected '%s' in format expression", signToken);
}
// Default message argument.
- // Alphabetic edit descriptor names are one or two characters in length.
+ // Alphabetic edit descriptor names are one to three characters in length.
argString_[0] = toupper(format_[token_.offset()]);
- argString_[1] = token_.length() > 1 ? toupper(*cursor_) : 0;
+ if (token_.length() > 2) {
+ // Three-character descriptor names (e.g., LZP, LZS).
+ // token_.offset() has the first character and *cursor_ has the last;
+ // find the middle character by scanning past any blanks.
+ const CHAR *mid{format_ + token_.offset() + 1};
+ while (mid < cursor_ && IsWhite(*mid)) {
+ ++mid;
+ }
+ argString_[1] = toupper(*mid);
+ argString_[2] = toupper(*cursor_);
+ } else {
+ argString_[1] = token_.length() > 1 ? toupper(*cursor_) : 0;
+ argString_[2] = 0;
+ }
// Process one format edit descriptor or do format list management.
switch (token_.kind()) {
case TokenKind::A:
@@ -794,6 +825,9 @@ template <typename CHAR> bool FormatValidator<CHAR>::Check() {
case TokenKind::BZ:
case TokenKind::DC:
case TokenKind::DP:
+ case TokenKind::LZ:
+ case TokenKind::LZS:
+ case TokenKind::LZP:
case TokenKind::RC:
case TokenKind::RD:
case TokenKind::RN:
@@ -807,6 +841,7 @@ template <typename CHAR> bool FormatValidator<CHAR>::Check() {
// R1318 blank-interp-edit-desc -> BN | BZ
// R1319 round-edit-desc -> RU | RD | RZ | RN | RC | RP
// R1320 decimal-edit-desc -> DC | DP
+ // F202X leading-zero-edit-desc -> LZ | LZS | LZP
check_r(false);
NextToken();
break;
diff --git a/flang/include/flang/Parser/format-specification.h b/flang/include/flang/Parser/format-specification.h
index 28c8affd7bde0..5d37a9c2c0060 100644
--- a/flang/include/flang/Parser/format-specification.h
+++ b/flang/include/flang/Parser/format-specification.h
@@ -95,6 +95,9 @@ struct ControlEditDesc {
RP,
DC,
DP,
+ LZ, // F202X: processor-dependent leading zero, default
+ LZS, // F202X: suppress leading zeros
+ LZP, // F202X: print leading zero
Dollar, // extension: inhibit newline on output
Backslash, // ditto, but only on terminals
};
diff --git a/flang/lib/Parser/io-parsers.cpp b/flang/lib/Parser/io-parsers.cpp
index cb3e68a05c94d..9da8c4f01d7dc 100644
--- a/flang/lib/Parser/io-parsers.cpp
+++ b/flang/lib/Parser/io-parsers.cpp
@@ -629,7 +629,8 @@ TYPE_PARSER(construct<format::IntrinsicTypeDataEditDesc>(
"X " >> pure(format::IntrinsicTypeDataEditDesc::Kind::EX) ||
pure(format::IntrinsicTypeDataEditDesc::Kind::E)) ||
"G " >> pure(format::IntrinsicTypeDataEditDesc::Kind::G) ||
- "L " >> pure(format::IntrinsicTypeDataEditDesc::Kind::L),
+ ("L "_tok / !letter /* don't occlude LZ, LZS, & LZP */) >>
+ pure(format::IntrinsicTypeDataEditDesc::Kind::L),
noInt, noInt, noInt)))
// R1307 data-edit-desc (part 2 of 2)
@@ -677,6 +678,12 @@ TYPE_PARSER(construct<format::ControlEditDesc>(
pure(format::ControlEditDesc::Kind::BN)) ||
"Z " >> construct<format::ControlEditDesc>(
pure(format::ControlEditDesc::Kind::BZ))) ||
+ "L " >> ("Z " >> ("S " >> construct<format::ControlEditDesc>(
+ pure(format::ControlEditDesc::Kind::LZS)) ||
+ "P " >> construct<format::ControlEditDesc>(
+ pure(format::ControlEditDesc::Kind::LZP)) ||
+ construct<format::ControlEditDesc>(
+ pure(format::ControlEditDesc::Kind::LZ)))) ||
"R " >> ("U " >> construct<format::ControlEditDesc>(
pure(format::ControlEditDesc::Kind::RU)) ||
"D " >> construct<format::ControlEditDesc>(
diff --git a/flang/lib/Parser/unparse.cpp b/flang/lib/Parser/unparse.cpp
index 3d8ea9f703b2f..8ad1f9b8ff618 100644
--- a/flang/lib/Parser/unparse.cpp
+++ b/flang/lib/Parser/unparse.cpp
@@ -1549,6 +1549,9 @@ class UnparseVisitor {
FMT(RP);
FMT(DC);
FMT(DP);
+ FMT(LZ);
+ FMT(LZS);
+ FMT(LZP);
#undef FMT
case format::ControlEditDesc::Kind::Dollar:
Put('$');
diff --git a/flang/test/Semantics/io16.f90 b/flang/test/Semantics/io16.f90
new file mode 100644
index 0000000000000..559d98f0d5ceb
--- /dev/null
+++ b/flang/test/Semantics/io16.f90
@@ -0,0 +1,99 @@
+! RUN: %python %S/test_errors.py %s %flang_fc1
+
+! F202X leading-zero control edit descriptors: LZ, LZS, LZP
+
+ ! Valid uses of LZ, LZP, LZS in FORMAT statements
+1001 format(LZ, F10.3)
+1002 format(LZP, F10.3)
+1003 format(LZS, F10.3)
+1004 format(LZ, E10.3)
+1005 format(LZP, E10.3)
+1006 format(LZS, E10.3)
+1007 format(LZS, D10.3)
+1008 format(LZ, G10.3)
+
+ ! Valid uses with blanks inside keywords (Fortran ignores blanks)
+1009 format(L Z, F10.3)
+1010 format(L Z P, F10.3)
+1011 format(L Z S, F10.3)
+
+ ! Combining with other control edit descriptors
+1012 format(LZP, DC, F10.3)
+1013 format(BN, LZS, F10.3)
+1014 format(LZ, SS, RZ, F10.3)
+
+ ! Multiple groups
+1015 format(LZP, 3F10.3, LZS, 2E12.4)
+
+ ! C1302 : multiple edit descriptors without ',' separation; no errors
+1016 format(LZF10.3)
+1017 format(LZPF10.3)
+1018 format(LZSF10.3)
+1019 format(LZE10.3)
+1020 format(LZPE10.3)
+1021 format(LZSD10.3)
+1022 format(LZG10.3)
+1023 format(LZPDCF10.3)
+1024 format(BNLZSF10.3)
+1025 format(LZPF10.3LZSF10.3)
+1026 format(LZP3F10.3LZS2E12.4)
+
+ ! In WRITE format strings
+ write(*, '(LZ, F10.3)') 0.5
+ write(*, '(LZP, F10.3)') 0.5
+ write(*, '(LZS, F10.3)') 0.5
+ write(*, '(LZP,E10.3)') 0.5
+ write(*, '(LZS,D10.3)') 0.5
+
+ ! C1302 : WRITE format strings without ',' separation; no errors
+ write(*, '(LZF10.3)') 0.5
+ write(*, '(LZPF10.3)') 0.5
+ write(*, '(LZSF10.3)') 0.5
+ write(*, '(LZPE10.3)') 0.5
+ write(*, '(LZP3F10.3LZS2E12.4)') 0.5, 0.5, 0.5, 0.5, 0.5
+
+ ! FMT= specifier with comma-separated descriptors
+ write(*, fmt='(LZ, F10.3)') 0.5
+ write(*, fmt='(LZP, F10.3)') 0.5
+ write(*, fmt='(LZS, F10.3)') 0.5
+ write(*, fmt='(LZP, E10.3)') 0.5
+ write(*, fmt='(LZS, D10.3)') 0.5
+ write(*, fmt='(LZP, DC, F10.3)') 0.5
+ write(*, fmt='(BN, LZS, F10.3)') 0.5
+
+ ! FMT= specifier without ',' separation; no errors
+ write(*, fmt='(LZF10.3)') 0.5
+ write(*, fmt='(LZPF10.3)') 0.5
+ write(*, fmt='(LZSF10.3)') 0.5
+ write(*, fmt='(LZPE10.3)') 0.5
+ write(*, fmt='(LZP3F10.3LZS2E12.4)') 0.5, 0.5, 0.5, 0.5, 0.5
+
+ ! FMT= specifier with FORMAT label reference
+ write(*, fmt=1001) 0.5
+ write(*, fmt=1002) 0.5
+ write(*, fmt=1017) 0.5
+
+ ! LZ/LZP/LZS coexisting with abbreviated L (no width) data edit descriptor
+ write(*, '(LZP, F10.3, L)') 0.5, .true.
+ write(*, '(LZS, F10.3, L)') 0.5, .true.
+
+ ! Error: repeat specifier before LZ/LZP/LZS in WRITE format strings
+ !ERROR: Repeat specifier before 'LZ' edit descriptor
+ write(*, '(3LZ, F10.3)') 0.5
+
+ !ERROR: Repeat specifier before 'LZP' edit descriptor
+ write(*, '(2LZP, F10.3)') 0.5
+
+ !ERROR: Repeat specifier before 'LZS' edit descriptor
+ write(*, '(2LZS, F10.3)') 0.5
+
+ ! Error: repeat specifier before LZ/LZP/LZS in FORMAT statements
+ !ERROR: Repeat specifier before 'LZ' edit descriptor
+2001 format(3LZ, F10.3)
+
+ !ERROR: Repeat specifier before 'LZP' edit descriptor
+2002 format(2LZP, F10.3)
+
+ !ERROR: Repeat specifier before 'LZS' edit descriptor
+2003 format(2LZS, F10.3)
+end
|
Member
|
@llvm/pr-subscribers-flang-parser Author: None (laoshd) Changes…control edit descriptors LZ, LZS, and LZP for formatted output (F, E, D, and G editing): LZ: processor-dependent (default, flang prints leading zero); LZS: suppress the optional leading zero before the decimal point; LZP: print the optional leading zero before the decimal point. Changes span the source parser, compile-time format validator, runtime format processing, and runtime output formatting. Includes semantic test (io16.f90) and documentation updates. Full diff: https://github.com/llvm/llvm-project/pull/183500.diff 10 Files Affected:
diff --git a/flang-rt/include/flang-rt/runtime/format-implementation.h b/flang-rt/include/flang-rt/runtime/format-implementation.h
index d510adbb5ba46..8b341def2b3ce 100644
--- a/flang-rt/include/flang-rt/runtime/format-implementation.h
+++ b/flang-rt/include/flang-rt/runtime/format-implementation.h
@@ -193,7 +193,7 @@ static RT_API_ATTRS bool AbsoluteTabbing(CONTEXT &context, int n) {
template <typename CONTEXT>
static RT_API_ATTRS void HandleControl(
- CONTEXT &context, char ch, char next, int n) {
+ CONTEXT &context, char ch, char next, int n, char next2 = '\0') {
MutableModes &modes{context.mutableModes()};
switch (ch) {
case 'B':
@@ -251,6 +251,21 @@ static RT_API_ATTRS void HandleControl(
return;
}
break;
+ case 'L':
+ if (next == 'Z') {
+ if (next2 == 'S') {
+ // LZS - suppress leading zeros
+ modes.leadingZero = MutableModes::LeadingZeroMode::Suppress;
+ } else if (next2 == 'P') {
+ // LZP - print leading zero
+ modes.leadingZero = MutableModes::LeadingZeroMode::Print;
+ } else {
+ // LZ - processor-dependent (default behavior)
+ modes.leadingZero = MutableModes::LeadingZeroMode::Processor;
+ }
+ return;
+ }
+ break;
case 'S':
if (next == 'P') {
modes.editingFlags |= signPlus;
@@ -455,6 +470,7 @@ RT_API_ATTRS int FormatControl<CONTEXT>::CueUpNextDataEdit(
} else if (ch >= 'A' && ch <= 'Z') {
int start{offset_ - 1};
CharType next{'\0'};
+ CharType next2{'\0'};
if (ch != 'P') { // 1PE5.2 - comma not required (C1302)
CharType peek{Capitalize(PeekNext())};
if (peek >= 'A' && peek <= 'Z') {
@@ -464,6 +480,15 @@ RT_API_ATTRS int FormatControl<CONTEXT>::CueUpNextDataEdit(
// Assume a two-letter edit descriptor
next = peek;
++offset_;
+ } else if (ch == 'L' && peek == 'Z') {
+ // LZ, LZS, or LZP control edit descriptor
+ next = peek;
+ ++offset_;
+ CharType peek2{Capitalize(PeekNext())};
+ if (peek2 == 'S' || peek2 == 'P') {
+ next2 = peek2;
+ ++offset_;
+ }
} else {
// extension: assume a comma between 'ch' and 'peek'
}
@@ -484,7 +509,7 @@ RT_API_ATTRS int FormatControl<CONTEXT>::CueUpNextDataEdit(
repeat = GetIntField(context);
}
HandleControl(context, static_cast<char>(ch), static_cast<char>(next),
- repeat ? *repeat : 1);
+ repeat ? *repeat : 1, static_cast<char>(next2));
}
} else if (ch == '/') {
context.AdvanceRecord(repeat && *repeat > 0 ? *repeat : 1);
diff --git a/flang-rt/include/flang-rt/runtime/format.h b/flang-rt/include/flang-rt/runtime/format.h
index 79a7dd713b1a1..787772935ce8c 100644
--- a/flang-rt/include/flang-rt/runtime/format.h
+++ b/flang-rt/include/flang-rt/runtime/format.h
@@ -44,6 +44,12 @@ struct MutableModes {
return editingFlags & decimalComma ? char32_t{','} : char32_t{'.'};
}
+ enum class LeadingZeroMode : std::uint8_t {
+ Processor, // LZ: processor-dependent (default)
+ Suppress, // LZS: suppress optional leading zero
+ Print, // LZP: print optional leading zero
+ };
+
std::uint8_t editingFlags{0}; // BN, DP, SS
enum decimal::FortranRounding round{
executionEnvironment
@@ -53,6 +59,7 @@ struct MutableModes {
short scale{0}; // kP
bool inNamelist{false}; // skip ! comments
bool nonAdvancing{false}; // ADVANCE='NO', or $ or \ in FORMAT
+ LeadingZeroMode leadingZero{LeadingZeroMode::Processor}; // LZ/LZS/LZP
};
// A single edit descriptor extracted from a FORMAT
diff --git a/flang-rt/lib/runtime/edit-output.cpp b/flang-rt/lib/runtime/edit-output.cpp
index 73dba35ff08d9..d0aa8638102a9 100644
--- a/flang-rt/lib/runtime/edit-output.cpp
+++ b/flang-rt/lib/runtime/edit-output.cpp
@@ -411,10 +411,26 @@ RT_API_ATTRS bool RealOutputEditing<KIND>::EditEorDOutput(
if (totalLength > width || !exponent) {
return EmitRepeated(io_, '*', width);
}
- if (totalLength < width && digitsBeforePoint == 0 &&
- zeroesBeforePoint == 0) {
- zeroesBeforePoint = 1;
- ++totalLength;
+ if (digitsBeforePoint == 0 && zeroesBeforePoint == 0 && scale <= 0) {
+ // Optional leading zero position (F202X leading zero control).
+ // When scale > 0 (kP with k > 0), digits are moved before the decimal
+ // point, so the leading zero position is not optional -- skip this.
+ // Value has no digits before the decimal point: "0.xxxE+yy" vs ".xxxE+yy"
+ switch (edit.modes.leadingZero) {
+ case MutableModes::LeadingZeroMode::Print:
+ // LZP: always print the optional leading zero
+ zeroesBeforePoint = 1;
+ ++totalLength;
+ break;
+ case MutableModes::LeadingZeroMode::Suppress:
+ // LZS: never print the optional leading zero
+ break;
+ case MutableModes::LeadingZeroMode::Processor:
+ // LZ: processor-defined; flang chooses to print it
+ zeroesBeforePoint = 1;
+ ++totalLength;
+ break;
+ }
}
if (totalLength < width && editWidth == 0) {
width = totalLength;
@@ -544,7 +560,24 @@ RT_API_ATTRS bool RealOutputEditing<KIND>::EditFOutput(const DataEdit &edit) {
if (digitsBeforePoint + zeroesBeforePoint + zeroesAfterPoint +
digitsAfterPoint + trailingZeroes ==
0) {
- zeroesBeforePoint = 1; // "." -> "0."
+ zeroesBeforePoint = 1; // "."--> "0." (bare decimal point)
+ } else if (digitsBeforePoint == 0 && zeroesBeforePoint == 0 &&
+ expo <= 0) {
+ // Optional leading zero position (F202X leading zero control).
+ // Value magnitude < 1: "0.xxx" vs ".xxx"
+ switch (edit.modes.leadingZero) {
+ case MutableModes::LeadingZeroMode::Print:
+ // LZP: always print the optional leading zero
+ zeroesBeforePoint = 1;
+ break;
+ case MutableModes::LeadingZeroMode::Suppress:
+ // LZS: never print the optional leading zero
+ break;
+ case MutableModes::LeadingZeroMode::Processor:
+ // LZ: processor-defined; flang chooses to print it
+ zeroesBeforePoint = 1;
+ break;
+ }
}
int totalLength{signLength + digitsBeforePoint + zeroesBeforePoint +
1 /*'.'*/ + zeroesAfterPoint + digitsAfterPoint + trailingZeroes +
@@ -553,10 +586,6 @@ RT_API_ATTRS bool RealOutputEditing<KIND>::EditFOutput(const DataEdit &edit) {
if (totalLength > width) {
return EmitRepeated(io_, '*', width);
}
- if (totalLength < width && digitsBeforePoint + zeroesBeforePoint == 0) {
- zeroesBeforePoint = 1;
- ++totalLength;
- }
return EmitPrefix(edit, totalLength, width) &&
EmitAscii(io_, convertedStr, signLength + digitsBeforePoint) &&
EmitRepeated(io_, '0', zeroesBeforePoint) &&
diff --git a/flang/docs/F202X.md b/flang/docs/F202X.md
index d1940a1858db1..6a303981cf264 100644
--- a/flang/docs/F202X.md
+++ b/flang/docs/F202X.md
@@ -261,6 +261,15 @@ The `AT` edit descriptor automatically trims character output. The `LZP`,
`LZS`, and `LZ` control edit descriptors and `LEADING_ZERO=` specifier provide a
means for controlling the output of leading zero digits.
+Implementation status:
+- `LZ`, `LZS`, `LZP` control edit descriptors, affect only F, E, D, and G
+ editing of an output statement: Implemented
+ - `LZ` - Processor-dependent, default (e.g., `0.2`)
+ - `LZS` - Suppress leading zeros (e.g., `.2`)
+ - `LZP` - Print leading zero (e.g. `0.2`)
+- `AT` edit descriptor: Not yet implemented
+- `LEADING_ZERO=specifier` in OPEN statement: Not yet implemented
+
#### Intrinsic Module Extensions
Addressing some issues and omissions in intrinsic modules:
diff --git a/flang/docs/FortranStandardsSupport.md b/flang/docs/FortranStandardsSupport.md
index f57956cd6d6b8..02e4653280f12 100644
--- a/flang/docs/FortranStandardsSupport.md
+++ b/flang/docs/FortranStandardsSupport.md
@@ -48,7 +48,7 @@ status of all important Fortran 2023 features. The table entries are based on th
| Extensions for c_f_pointer intrinsic | Y | |
| Procedures for converting between fortran and c strings | N | |
| The at edit descriptor | N | |
-| Control over leading zeros in output of real values | N | |
+| Control over leading zeros in output of real values | P | LZ/LZS/LZP edit descriptors implemented; LEADING_ZERO=specifier not yet implemented |
| Extensions for Namelist | N | |
| Allow an object of a type with a coarray ultimate component to be an array or allocatable | N | |
| Put with Notify | N | |
diff --git a/flang/include/flang/Common/format.h b/flang/include/flang/Common/format.h
index 1e64acb823616..60bcc8e81ee38 100644
--- a/flang/include/flang/Common/format.h
+++ b/flang/include/flang/Common/format.h
@@ -114,7 +114,7 @@ struct FormatMessage {
// This declaration is logically private to class FormatValidator.
// It is placed here to work around a clang compilation problem.
ENUM_CLASS(TokenKind, None, A, B, BN, BZ, D, DC, DP, DT, E, EN, ES, EX, F, G, I,
- L, O, P, RC, RD, RN, RP, RU, RZ, S, SP, SS, T, TL, TR, X, Z, Colon, Slash,
+ L, LZ, LZP, LZS, O, P, RC, RD, RN, RP, RU, RZ, S, SP, SS, T, TL, TR, X, Z, Colon, Slash,
Backslash, // nonstandard: inhibit newline on output
Dollar, // nonstandard: inhibit newline on output on terminals
Star, LParen, RParen, Comma, Point, Sign,
@@ -219,7 +219,7 @@ template <typename CHAR = char> class FormatValidator {
std::int64_t knrValue_{-1}; // -1 ==> not present
std::int64_t scaleFactorValue_{}; // signed k in kP
std::int64_t wValue_{-1};
- char argString_[3]{}; // 1-2 character msg arg; usually edit descriptor name
+ char argString_[4]{}; // 1-3 character msg arg; usually edit descriptor name
bool formatHasErrors_{false};
bool unterminatedFormatError_{false};
bool suppressMessageCascade_{false};
@@ -390,7 +390,25 @@ template <typename CHAR> void FormatValidator<CHAR>::NextToken() {
token_.set_kind(TokenKind::I);
break;
case 'L':
- token_.set_kind(TokenKind::L);
+ switch (LookAheadChar()) {
+ case 'Z':
+ // Advance past 'Z', then look ahead for 'S' or 'P'
+ Advance(TokenKind::LZ);
+ switch (LookAheadChar()) {
+ case 'S':
+ Advance(TokenKind::LZS);
+ break;
+ case 'P':
+ Advance(TokenKind::LZP);
+ break;
+ default:
+ break;
+ }
+ break;
+ default:
+ token_.set_kind(TokenKind::L);
+ break;
+ }
break;
case 'O':
token_.set_kind(TokenKind::O);
@@ -674,9 +692,22 @@ template <typename CHAR> bool FormatValidator<CHAR>::Check() {
ReportError("Unexpected '%s' in format expression", signToken);
}
// Default message argument.
- // Alphabetic edit descriptor names are one or two characters in length.
+ // Alphabetic edit descriptor names are one to three characters in length.
argString_[0] = toupper(format_[token_.offset()]);
- argString_[1] = token_.length() > 1 ? toupper(*cursor_) : 0;
+ if (token_.length() > 2) {
+ // Three-character descriptor names (e.g., LZP, LZS).
+ // token_.offset() has the first character and *cursor_ has the last;
+ // find the middle character by scanning past any blanks.
+ const CHAR *mid{format_ + token_.offset() + 1};
+ while (mid < cursor_ && IsWhite(*mid)) {
+ ++mid;
+ }
+ argString_[1] = toupper(*mid);
+ argString_[2] = toupper(*cursor_);
+ } else {
+ argString_[1] = token_.length() > 1 ? toupper(*cursor_) : 0;
+ argString_[2] = 0;
+ }
// Process one format edit descriptor or do format list management.
switch (token_.kind()) {
case TokenKind::A:
@@ -794,6 +825,9 @@ template <typename CHAR> bool FormatValidator<CHAR>::Check() {
case TokenKind::BZ:
case TokenKind::DC:
case TokenKind::DP:
+ case TokenKind::LZ:
+ case TokenKind::LZS:
+ case TokenKind::LZP:
case TokenKind::RC:
case TokenKind::RD:
case TokenKind::RN:
@@ -807,6 +841,7 @@ template <typename CHAR> bool FormatValidator<CHAR>::Check() {
// R1318 blank-interp-edit-desc -> BN | BZ
// R1319 round-edit-desc -> RU | RD | RZ | RN | RC | RP
// R1320 decimal-edit-desc -> DC | DP
+ // F202X leading-zero-edit-desc -> LZ | LZS | LZP
check_r(false);
NextToken();
break;
diff --git a/flang/include/flang/Parser/format-specification.h b/flang/include/flang/Parser/format-specification.h
index 28c8affd7bde0..5d37a9c2c0060 100644
--- a/flang/include/flang/Parser/format-specification.h
+++ b/flang/include/flang/Parser/format-specification.h
@@ -95,6 +95,9 @@ struct ControlEditDesc {
RP,
DC,
DP,
+ LZ, // F202X: processor-dependent leading zero, default
+ LZS, // F202X: suppress leading zeros
+ LZP, // F202X: print leading zero
Dollar, // extension: inhibit newline on output
Backslash, // ditto, but only on terminals
};
diff --git a/flang/lib/Parser/io-parsers.cpp b/flang/lib/Parser/io-parsers.cpp
index cb3e68a05c94d..9da8c4f01d7dc 100644
--- a/flang/lib/Parser/io-parsers.cpp
+++ b/flang/lib/Parser/io-parsers.cpp
@@ -629,7 +629,8 @@ TYPE_PARSER(construct<format::IntrinsicTypeDataEditDesc>(
"X " >> pure(format::IntrinsicTypeDataEditDesc::Kind::EX) ||
pure(format::IntrinsicTypeDataEditDesc::Kind::E)) ||
"G " >> pure(format::IntrinsicTypeDataEditDesc::Kind::G) ||
- "L " >> pure(format::IntrinsicTypeDataEditDesc::Kind::L),
+ ("L "_tok / !letter /* don't occlude LZ, LZS, & LZP */) >>
+ pure(format::IntrinsicTypeDataEditDesc::Kind::L),
noInt, noInt, noInt)))
// R1307 data-edit-desc (part 2 of 2)
@@ -677,6 +678,12 @@ TYPE_PARSER(construct<format::ControlEditDesc>(
pure(format::ControlEditDesc::Kind::BN)) ||
"Z " >> construct<format::ControlEditDesc>(
pure(format::ControlEditDesc::Kind::BZ))) ||
+ "L " >> ("Z " >> ("S " >> construct<format::ControlEditDesc>(
+ pure(format::ControlEditDesc::Kind::LZS)) ||
+ "P " >> construct<format::ControlEditDesc>(
+ pure(format::ControlEditDesc::Kind::LZP)) ||
+ construct<format::ControlEditDesc>(
+ pure(format::ControlEditDesc::Kind::LZ)))) ||
"R " >> ("U " >> construct<format::ControlEditDesc>(
pure(format::ControlEditDesc::Kind::RU)) ||
"D " >> construct<format::ControlEditDesc>(
diff --git a/flang/lib/Parser/unparse.cpp b/flang/lib/Parser/unparse.cpp
index 3d8ea9f703b2f..8ad1f9b8ff618 100644
--- a/flang/lib/Parser/unparse.cpp
+++ b/flang/lib/Parser/unparse.cpp
@@ -1549,6 +1549,9 @@ class UnparseVisitor {
FMT(RP);
FMT(DC);
FMT(DP);
+ FMT(LZ);
+ FMT(LZS);
+ FMT(LZP);
#undef FMT
case format::ControlEditDesc::Kind::Dollar:
Put('$');
diff --git a/flang/test/Semantics/io16.f90 b/flang/test/Semantics/io16.f90
new file mode 100644
index 0000000000000..559d98f0d5ceb
--- /dev/null
+++ b/flang/test/Semantics/io16.f90
@@ -0,0 +1,99 @@
+! RUN: %python %S/test_errors.py %s %flang_fc1
+
+! F202X leading-zero control edit descriptors: LZ, LZS, LZP
+
+ ! Valid uses of LZ, LZP, LZS in FORMAT statements
+1001 format(LZ, F10.3)
+1002 format(LZP, F10.3)
+1003 format(LZS, F10.3)
+1004 format(LZ, E10.3)
+1005 format(LZP, E10.3)
+1006 format(LZS, E10.3)
+1007 format(LZS, D10.3)
+1008 format(LZ, G10.3)
+
+ ! Valid uses with blanks inside keywords (Fortran ignores blanks)
+1009 format(L Z, F10.3)
+1010 format(L Z P, F10.3)
+1011 format(L Z S, F10.3)
+
+ ! Combining with other control edit descriptors
+1012 format(LZP, DC, F10.3)
+1013 format(BN, LZS, F10.3)
+1014 format(LZ, SS, RZ, F10.3)
+
+ ! Multiple groups
+1015 format(LZP, 3F10.3, LZS, 2E12.4)
+
+ ! C1302 : multiple edit descriptors without ',' separation; no errors
+1016 format(LZF10.3)
+1017 format(LZPF10.3)
+1018 format(LZSF10.3)
+1019 format(LZE10.3)
+1020 format(LZPE10.3)
+1021 format(LZSD10.3)
+1022 format(LZG10.3)
+1023 format(LZPDCF10.3)
+1024 format(BNLZSF10.3)
+1025 format(LZPF10.3LZSF10.3)
+1026 format(LZP3F10.3LZS2E12.4)
+
+ ! In WRITE format strings
+ write(*, '(LZ, F10.3)') 0.5
+ write(*, '(LZP, F10.3)') 0.5
+ write(*, '(LZS, F10.3)') 0.5
+ write(*, '(LZP,E10.3)') 0.5
+ write(*, '(LZS,D10.3)') 0.5
+
+ ! C1302 : WRITE format strings without ',' separation; no errors
+ write(*, '(LZF10.3)') 0.5
+ write(*, '(LZPF10.3)') 0.5
+ write(*, '(LZSF10.3)') 0.5
+ write(*, '(LZPE10.3)') 0.5
+ write(*, '(LZP3F10.3LZS2E12.4)') 0.5, 0.5, 0.5, 0.5, 0.5
+
+ ! FMT= specifier with comma-separated descriptors
+ write(*, fmt='(LZ, F10.3)') 0.5
+ write(*, fmt='(LZP, F10.3)') 0.5
+ write(*, fmt='(LZS, F10.3)') 0.5
+ write(*, fmt='(LZP, E10.3)') 0.5
+ write(*, fmt='(LZS, D10.3)') 0.5
+ write(*, fmt='(LZP, DC, F10.3)') 0.5
+ write(*, fmt='(BN, LZS, F10.3)') 0.5
+
+ ! FMT= specifier without ',' separation; no errors
+ write(*, fmt='(LZF10.3)') 0.5
+ write(*, fmt='(LZPF10.3)') 0.5
+ write(*, fmt='(LZSF10.3)') 0.5
+ write(*, fmt='(LZPE10.3)') 0.5
+ write(*, fmt='(LZP3F10.3LZS2E12.4)') 0.5, 0.5, 0.5, 0.5, 0.5
+
+ ! FMT= specifier with FORMAT label reference
+ write(*, fmt=1001) 0.5
+ write(*, fmt=1002) 0.5
+ write(*, fmt=1017) 0.5
+
+ ! LZ/LZP/LZS coexisting with abbreviated L (no width) data edit descriptor
+ write(*, '(LZP, F10.3, L)') 0.5, .true.
+ write(*, '(LZS, F10.3, L)') 0.5, .true.
+
+ ! Error: repeat specifier before LZ/LZP/LZS in WRITE format strings
+ !ERROR: Repeat specifier before 'LZ' edit descriptor
+ write(*, '(3LZ, F10.3)') 0.5
+
+ !ERROR: Repeat specifier before 'LZP' edit descriptor
+ write(*, '(2LZP, F10.3)') 0.5
+
+ !ERROR: Repeat specifier before 'LZS' edit descriptor
+ write(*, '(2LZS, F10.3)') 0.5
+
+ ! Error: repeat specifier before LZ/LZP/LZS in FORMAT statements
+ !ERROR: Repeat specifier before 'LZ' edit descriptor
+2001 format(3LZ, F10.3)
+
+ !ERROR: Repeat specifier before 'LZP' edit descriptor
+2002 format(2LZP, F10.3)
+
+ !ERROR: Repeat specifier before 'LZS' edit descriptor
+2003 format(2LZS, F10.3)
+end
|
Contributor
|
@laoshd , could you please also add flang-rt tests for the new edit descriptors? Also, it may be a good idea to also add some execution tests to llvm-test-suite. |
|
✅ With the latest revision this PR passed the C/C++ code formatter. |
🪟 Windows x64 Test Results
✅ The build succeeded and all tests passed. |
🐧 Linux x64 Test Results
✅ The build succeeded and all tests passed. |
…zero control edit descriptors in FORMAT statements, flang/test/Semantics/io17.f90. Previously added io16.f90 was used.
Contributor
Author
This test failure is a from an existing issue: #183581 |
Contributor
|
Can you update the title of your PR so it fits in? |
laoshd
changed the title
… and docs format; Add flang-rt test, LeadingZeroTest.cpp.
Contributor
Author
Updated. |
Contributor
Author
A flang-rt test has been added. I'll add execution test to llvm-test-suite in a separated PR. Will that work? Please let me know if the execution has also to be added in this PR. Thanks. |
Contributor
Author
I have updated the title. Please advise if I still missed something. Thanks. |
Contributor
Please read the instructions regarding commit messages in the LLVM Developer Policy. Your title does not adhere to the guidelines. You can also look at other commit messages in the flang subdirectory to get a sense for what this should look like. Please address the failures in the pre-commit CI below. |
Contributor
I think it is worse than before. You can just have |
laoshd
changed the title
Contributor
Author
|
Contributor
Author
|
Contributor
Author
Updated. |
This was referenced Feb 28, 2026
eugeneepshteyn
pushed a commit
that referenced
this pull request
Mar 5, 2026
…lve conflict: io17.f90 has been used.
Contributor
Author
Fixed by the merge of PR #183878. |
Contributor
Author
Fixed by the merge of PR #183878 |
Contributor
Author
The Flang.Semantics test failures were fixed by the merge of PR #183878 |
klausler
reviewed
Mar 11, 2026
| // LZP - print leading zero | ||
| modes.leadingZero = MutableModes::LeadingZeroMode::Print; | ||
| } else { | ||
| // LZ - processor-dependent (default behavior) |
Contributor
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Why is there a distinct enumeration for LZ? It always maps to one of the other two settings.
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LZP will always print the leading zero, LZS will never print, LZ will print or not depending on "processor-defined". This three-way distinction matches the standard's intent.
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"The leading zero mode controls optional leading zero characters in numeric output fields. When the leading zero
mode is PRINT, the processor shall produce a leading zero in any position that normally contains an optional
leading zero. When the leading zero mode is SUPPRESS, the processor shall not produce a leading zero in such
positions. When the leading zero mode is PROCESSOR_DEFINED, the processor has the option of producing
a leading zero or not in such positions, subject to 13.7.2(5)."
| template <typename CONTEXT> | ||
| static RT_API_ATTRS void HandleControl( | ||
| CONTEXT &context, char ch, char next, int n) { | ||
| CONTEXT &context, char ch, char next, int n, char next2 = '\0') { |
Contributor
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Are there calls to HandleControl() that need this default value for the new parameter?
Contributor
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Good catch. The default value is unnecessary. Will remove it.
| return editingFlags & decimalComma ? char32_t{','} : char32_t{'.'}; | ||
| } | ||
|
|
||
| enum class LeadingZeroMode : std::uint8_t { |
Contributor
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This could just be a new editing flag, like BN or DP.
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LZ/LZP/LZS is a three-way choice. It cannot be done by a flag.
Contributor
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LZ means either LZP or LZS, and those two only require one bit to distinguish them.
flang-rt/lib/runtime/edit-output.cpp
Outdated
| // point, so the leading zero position is not optional -- skip this. | ||
| // Value has no digits before the decimal point: "0.xxxE+yy" vs ".xxxE+yy" | ||
| switch (edit.modes.leadingZero) { | ||
| case MutableModes::LeadingZeroMode::Print: |
Contributor
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This isn't how the edit descriptors' behaviors are defined in 13.8.5. Please conform to the standard when adding new standard features. LZP should behave in the way that you defined LZ, and LZ should behave like LZS or LZP.
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My understanding of the standard is that: LZP means PRINT, alway prints the leading zero; LZS means SUPPRESS, never prints the leading zero; and LZ means PROCESSOR_DEFINED, the processor has option of printing or not (behavior the same as no leading zero edit descriptor is used).
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LZP prints a leading zero when there's room for it. LZS doesn't. LZ maps to one or the other of these.
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Ok. I re-implemented it with editingFlags replacing enum, and made it match this request. Would you review it again please.
flang-rt/lib/runtime/edit-output.cpp
Outdated
| // Optional leading zero position (F202X leading zero control). | ||
| // Value magnitude < 1: "0.xxx" vs ".xxx" | ||
| switch (edit.modes.leadingZero) { | ||
| case MutableModes::LeadingZeroMode::Print: |
Contributor
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See above. This is not how the modes are defined in the standard.
klausler
reviewed
Mar 12, 2026
| template <typename CONTEXT> | ||
| static RT_API_ATTRS void HandleControl( | ||
| CONTEXT &context, char ch, char next, int n) { | ||
| CONTEXT &context, char ch, char next, int n, char next2) { |
Contributor
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It seems odd that next2 is not the parameter immediately after next.
| digitsAfterPoint + trailingZeroes == | ||
| 0) { | ||
| zeroesBeforePoint = 1; // "." -> "0." | ||
| zeroesBeforePoint = 1; // "."--> "0." (bare decimal point) |
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"." would be a bare decimal point. "0." is not one.
| Implementation status: | ||
| - `LZ`, `LZS`, `LZP` control edit descriptors, affect only F, E, D, and G | ||
| editing of an output statement: Implemented | ||
| - `LZ` - Processor-dependent, default (e.g., `0.2`) |
Contributor
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Please note that this (LZ) is equivalent to LZP.
| editing of an output statement: Implemented | ||
| - `LZ` - Processor-dependent, default (e.g., `0.2`) | ||
| - `LZS` - Suppress leading zeros (e.g., `.2`) | ||
| - `LZP` - Print leading zero (e.g. `0.2`) |
Contributor
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A leading zero is printed only when there is room in the field for it.
| - `LZS` - Suppress leading zeros (e.g., `.2`) | ||
| - `LZP` - Print leading zero (e.g. `0.2`) | ||
| - `AT` edit descriptor: Not yet implemented | ||
| - `LEADING_ZERO=specifier` in OPEN statement: Not yet implemented |
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This OPEN control specifier should also be part of this change, I think.
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LZ: processor-dependent (default, flang prints leading zero); LZS: suppress the optional leading zero before the decimal point; LZP: print the optional leading zero before the decimal point. Changes span the source parser, compile-time format validator, runtime format processing, and runtime output formatting. Includes semantic test (io16.f90) and documentation updates.