Implement null dereference check

changelog/dmd.nullderefcheck.dd

@@ -0,0 +1,10 @@
+An optional check for null dereference is added
+
+A new check has been implemented that injects code to check a pointer for null before it is dereferenced.
+
+It will be typically be used if you need a backtrace generated (when one is not automatically done), or if you want to catch and handle the Error as part of a scheduler.
+
+This can be enabled by using ``-check=nullderef=on`` by default it is off.
+What happens may be customized by the ``-checkaction`` switch and by setting a new handler in ``core.exception``.
+
+Due to issues in dmd's backend, not all pointer dereferences are guaranteed to get a check.

compiler/src/dmd/backend/codebuilder.d

@@ -399,10 +399,7 @@ assert(op != BADINS);
     @trusted
     code* last()
     {
-        // g++ and clang++ complain about offsetof() because of the code::code() constructor.
-        // return (code *)((char *)pTail - offsetof(code, next));
-        // So do our own.
-        return cast(code*)(cast(void*)pTail - (cast(void*)&(*pTail).next - cast(void*)*pTail));
+        return cast(code*)(cast(void*)pTail - code.next.offsetof);
     }
 
     /*************************************

compiler/src/dmd/backend/drtlsym.d

@@ -89,6 +89,7 @@ Symbol* getRtlsym(RTLSYM i) @trusted
         case RTLSYM.DARRAYP:                symbolz(ps,FL.func,FREGSAVED,"_d_arrayboundsp", SFLexit, t); break;
         case RTLSYM.DARRAY_SLICEP:          symbolz(ps,FL.func,FREGSAVED,"_d_arraybounds_slicep", SFLexit, t); break;
         case RTLSYM.DARRAY_INDEXP:          symbolz(ps,FL.func,FREGSAVED,"_d_arraybounds_indexp", SFLexit, t); break;
+        case RTLSYM.DNULLP:                 symbolz(ps,FL.func,FREGSAVED,"_d_nullpointerp", SFLexit, t); break;
         case RTLSYM.DINVARIANT:             symbolz(ps,FL.func,FREGSAVED,"_D2rt10invariant_12_d_invariantFC6ObjectZv", 0, tsdlib); break;
         case RTLSYM.MEMCPY:                 symbolz(ps,FL.func,FREGSAVED,"memcpy",    0, t); break;
         case RTLSYM.MEMSET8:                symbolz(ps,FL.func,FREGSAVED,"memset",    0, t); break;

compiler/src/dmd/backend/rtlsym.d

@@ -33,6 +33,7 @@ enum RTLSYM
     DARRAYP,
     DARRAY_SLICEP,
     DARRAY_INDEXP,
+    DNULLP,
     DINVARIANT,
     MEMCPY,
     MEMSET8,

compiler/src/dmd/cli.d

@@ -1187,6 +1187,7 @@ struct CLIUsage
   =invariant[=[on|off]] Class/struct invariants
   =out[=[on|off]]       Out contracts
   =switch[=[on|off]]    Final switch failure checking
+  =nullderef[=[on|off]] Null dereference error
   =on                   Enable all assertion checking
                         (default for non-release builds)
   =off                  Disable all assertion checking

compiler/src/dmd/dfa/fast/report.d

@@ -71,7 +71,7 @@ struct DFAReporter
         }
     }
 
-    void onLoopyLabelLessNullThan(DFAVar* var, ref const(Loc) loc)
+    void onLoopyLabelLessNullThan(DFAVar* var, ref const Loc loc)
     {
         if (var !is null && !var.isModellable)
             return;
@@ -88,7 +88,7 @@ struct DFAReporter
      * to guarantee a non-null output, this ensures the variable is actually non-null
      * when the scope exits.
      */
-    void onEndOfScope(FuncDeclaration fd, ref Loc loc)
+    void onEndOfScope(FuncDeclaration fd, ref const Loc loc)
     {
         // this is where we validate escapes, for a specific location
 

compiler/src/dmd/dfa/fast/statement.d

@@ -603,7 +603,7 @@ final:
             // This signals that no code after this point in the current block is reachable.
             dfaCommon.currentDFAScope.haveJumped = true;
             dfaCommon.currentDFAScope.haveReturned = true;
-            analyzer.reporter.onEndOfScope(dfaCommon.currentFunction, exp.loc);
+            analyzer.reporter.onEndOfScope(dfaCommon.currentFunction, st.loc);
             break;
 
         case STMT.Compound:
@@ -895,6 +895,7 @@ final:
                 dfaCommon.currentDFAScope.inConditional = true;
                 dfaCommon.setScopeAsLoopyLabel;
 
+                if (theCondition !is null)
                 {
                     dfaCommon.printStructure((ref OutBuffer ob,
                             scope PrintPrefixType prefix) => ob.writestring("For condition:\n"));
@@ -909,6 +910,8 @@ final:
 
                     expWalker.seeAssert(lrCondition, theCondition.loc, true);
                 }
+                else
+                    dfaCommon.currentDFAScope.isLoopyLabelKnownToHaveRun = true;
 
                 dfaCommon.printStructure((ref OutBuffer ob,
                         scope PrintPrefixType prefix) => ob.writestring("For body:\n"));

compiler/src/dmd/frontend.h

@@ -8211,6 +8211,7 @@ struct Param final
     CHECKENABLE useIn;
     CHECKENABLE useOut;
     CHECKENABLE useArrayBounds;
+    CHECKENABLE useNullCheck;
     CHECKENABLE useAssert;
     CHECKENABLE useSwitchError;
     CHECKENABLE boundscheck;
@@ -8294,6 +8295,7 @@ struct Param final
         useIn((CHECKENABLE)0u),
         useOut((CHECKENABLE)0u),
         useArrayBounds((CHECKENABLE)0u),
+        useNullCheck((CHECKENABLE)0u),
         useAssert((CHECKENABLE)0u),
         useSwitchError((CHECKENABLE)0u),
         boundscheck((CHECKENABLE)0u),
@@ -8334,7 +8336,7 @@ struct Param final
         timeTraceFile()
     {
     }
-    Param(bool obj, bool readStdin = false, bool multiobj = false, bool trace = false, bool tracegc = false, bool vcg_ast = false, DiagnosticReporting useDeprecated = (DiagnosticReporting)1u, bool useUnitTests = false, bool useInline = false, bool release = false, bool preservePaths = false, DiagnosticReporting useWarnings = (DiagnosticReporting)2u, bool cov = false, uint8_t covPercent = 0u, bool ctfe_cov = false, bool ignoreUnsupportedPragmas = true, bool useModuleInfo = true, bool useTypeInfo = true, bool useExceptions = true, bool useGC = true, bool betterC = false, bool addMain = false, bool allInst = false, bool bitfields = true, bool rewriteNoExceptionToSeq = false, CppStdRevision cplusplus = (CppStdRevision)201103u, Help help = Help(), Verbose v = Verbose(), Edition edition = (Edition)2023u, void* editionFiles = nullptr, FeatureState useDIP25 = (FeatureState)2u, FeatureState useDIP1000 = (FeatureState)0u, bool ehnogc = false, bool useDIP1021 = false, FeatureState fieldwise = (FeatureState)0u, bool fixAliasThis = false, FeatureState rvalueRefParam = (FeatureState)0u, FeatureState safer = (FeatureState)0u, FeatureState noSharedAccess = (FeatureState)0u, bool previewIn = false, bool inclusiveInContracts = false, bool shortenedMethods = true, bool fixImmutableConv = false, bool fix16997 = true, FeatureState dtorFields = (FeatureState)0u, FeatureState systemVariables = (FeatureState)0u, bool useFastDFA = false, CHECKENABLE useInvariants = (CHECKENABLE)0u, CHECKENABLE useIn = (CHECKENABLE)0u, CHECKENABLE useOut = (CHECKENABLE)0u, CHECKENABLE useArrayBounds = (CHECKENABLE)0u, CHECKENABLE useAssert = (CHECKENABLE)0u, CHECKENABLE useSwitchError = (CHECKENABLE)0u, CHECKENABLE boundscheck = (CHECKENABLE)0u, CHECKACTION checkAction = (CHECKACTION)0u, CLIIdentifierTable dIdentifierTable = (CLIIdentifierTable)0u, CLIIdentifierTable cIdentifierTable = (CLIIdentifierTable)0u, _d_dynamicArray< const char > argv0 = {}, Array<const char* > modFileAliasStrings = Array<const char* >(), Array<ImportPathInfo > imppath = Array<ImportPathInfo >(), Array<const char* > fileImppath = Array<const char* >(), _d_dynamicArray< const char > objdir = {}, _d_dynamicArray< const char > objname = {}, _d_dynamicArray< const char > libname = {}, Output ddoc = Output(), Output dihdr = Output(), Output cxxhdr = Output(), Output json = Output(), JsonFieldFlags jsonFieldFlags = (JsonFieldFlags)0u, Output makeDeps = Output(), Output mixinOut = Output(), Output moduleDeps = Output(), bool debugEnabled = false, bool run = false, Array<const char* > runargs = Array<const char* >(), Array<const char* > cppswitches = Array<const char* >(), const char* cpp = nullptr, Array<const char* > objfiles = Array<const char* >(), Array<const char* > linkswitches = Array<const char* >(), Array<bool > linkswitchIsForCC = Array<bool >(), Array<const char* > libfiles = Array<const char* >(), Array<const char* > dllfiles = Array<const char* >(), _d_dynamicArray< const char > deffile = {}, _d_dynamicArray< const char > resfile = {}, _d_dynamicArray< const char > exefile = {}, _d_dynamicArray< const char > mapfile = {}, bool fullyQualifiedObjectFiles = false, bool timeTrace = false, uint32_t timeTraceGranularityUs = 500u, const char* timeTraceFile = nullptr) :
+    Param(bool obj, bool readStdin = false, bool multiobj = false, bool trace = false, bool tracegc = false, bool vcg_ast = false, DiagnosticReporting useDeprecated = (DiagnosticReporting)1u, bool useUnitTests = false, bool useInline = false, bool release = false, bool preservePaths = false, DiagnosticReporting useWarnings = (DiagnosticReporting)2u, bool cov = false, uint8_t covPercent = 0u, bool ctfe_cov = false, bool ignoreUnsupportedPragmas = true, bool useModuleInfo = true, bool useTypeInfo = true, bool useExceptions = true, bool useGC = true, bool betterC = false, bool addMain = false, bool allInst = false, bool bitfields = true, bool rewriteNoExceptionToSeq = false, CppStdRevision cplusplus = (CppStdRevision)201103u, Help help = Help(), Verbose v = Verbose(), Edition edition = (Edition)2023u, void* editionFiles = nullptr, FeatureState useDIP25 = (FeatureState)2u, FeatureState useDIP1000 = (FeatureState)0u, bool ehnogc = false, bool useDIP1021 = false, FeatureState fieldwise = (FeatureState)0u, bool fixAliasThis = false, FeatureState rvalueRefParam = (FeatureState)0u, FeatureState safer = (FeatureState)0u, FeatureState noSharedAccess = (FeatureState)0u, bool previewIn = false, bool inclusiveInContracts = false, bool shortenedMethods = true, bool fixImmutableConv = false, bool fix16997 = true, FeatureState dtorFields = (FeatureState)0u, FeatureState systemVariables = (FeatureState)0u, bool useFastDFA = false, CHECKENABLE useInvariants = (CHECKENABLE)0u, CHECKENABLE useIn = (CHECKENABLE)0u, CHECKENABLE useOut = (CHECKENABLE)0u, CHECKENABLE useArrayBounds = (CHECKENABLE)0u, CHECKENABLE useNullCheck = (CHECKENABLE)0u, CHECKENABLE useAssert = (CHECKENABLE)0u, CHECKENABLE useSwitchError = (CHECKENABLE)0u, CHECKENABLE boundscheck = (CHECKENABLE)0u, CHECKACTION checkAction = (CHECKACTION)0u, CLIIdentifierTable dIdentifierTable = (CLIIdentifierTable)0u, CLIIdentifierTable cIdentifierTable = (CLIIdentifierTable)0u, _d_dynamicArray< const char > argv0 = {}, Array<const char* > modFileAliasStrings = Array<const char* >(), Array<ImportPathInfo > imppath = Array<ImportPathInfo >(), Array<const char* > fileImppath = Array<const char* >(), _d_dynamicArray< const char > objdir = {}, _d_dynamicArray< const char > objname = {}, _d_dynamicArray< const char > libname = {}, Output ddoc = Output(), Output dihdr = Output(), Output cxxhdr = Output(), Output json = Output(), JsonFieldFlags jsonFieldFlags = (JsonFieldFlags)0u, Output makeDeps = Output(), Output mixinOut = Output(), Output moduleDeps = Output(), bool debugEnabled = false, bool run = false, Array<const char* > runargs = Array<const char* >(), Array<const char* > cppswitches = Array<const char* >(), const char* cpp = nullptr, Array<const char* > objfiles = Array<const char* >(), Array<const char* > linkswitches = Array<const char* >(), Array<bool > linkswitchIsForCC = Array<bool >(), Array<const char* > libfiles = Array<const char* >(), Array<const char* > dllfiles = Array<const char* >(), _d_dynamicArray< const char > deffile = {}, _d_dynamicArray< const char > resfile = {}, _d_dynamicArray< const char > exefile = {}, _d_dynamicArray< const char > mapfile = {}, bool fullyQualifiedObjectFiles = false, bool timeTrace = false, uint32_t timeTraceGranularityUs = 500u, const char* timeTraceFile = nullptr) :
         obj(obj),
         readStdin(readStdin),
         multiobj(multiobj),
@@ -8386,6 +8388,7 @@ struct Param final
         useIn(useIn),
         useOut(useOut),
         useArrayBounds(useArrayBounds),
+        useNullCheck(useNullCheck),
         useAssert(useAssert),
         useSwitchError(useSwitchError),
         boundscheck(boundscheck),

compiler/src/dmd/funcsem.d

@@ -4282,16 +4282,43 @@ bool arrayBoundsCheck(FuncDeclaration fd)
     case CHECKENABLE.on:
         return true;
     case CHECKENABLE.safeonly:
+        if (fd)
         {
+            Type t = fd.type;
+            if (t.isTypeFunction() && t.isTypeFunction().trust == TRUST.safe)
+                return true;
+        }
+        return false;
+    case CHECKENABLE._default:
+        assert(0);
+    }
+}
+
+/**********************
+ * Check to see if null dereference checking code has to be generated
+ *
+ * Params:
+ *  fd = function for which code is to be generated
+ * Returns:
+ *  true if do null dereference checking for the given function
+ */
+bool nullDerefCheck(FuncDeclaration fd)
+{
+    final switch (global.params.useNullCheck)
+    {
+        case CHECKENABLE.off:
+            return false;
+        case CHECKENABLE.on:
+            return true;
+        case CHECKENABLE.safeonly:
             if (fd)
             {
                 Type t = fd.type;
-                if (t.ty == Tfunction && (cast(TypeFunction)t).trust == TRUST.safe)
+                if (t.isTypeFunction() && t.isTypeFunction().trust == TRUST.safe)
                     return true;
             }
             return false;
-        }
-    case CHECKENABLE._default:
-        assert(0);
+        case CHECKENABLE._default:
+            assert(0);
     }
 }

compiler/src/dmd/globals.d

@@ -224,6 +224,7 @@ extern (C++) struct Param
     CHECKENABLE useIn          = CHECKENABLE._default;  // generate precondition checks
     CHECKENABLE useOut         = CHECKENABLE._default;  // generate postcondition checks
     CHECKENABLE useArrayBounds = CHECKENABLE._default;  // when to generate code for array bounds checks
+    CHECKENABLE useNullCheck   = CHECKENABLE._default;  // when to generate code for null dereference checks
     CHECKENABLE useAssert      = CHECKENABLE._default;  // when to generate code for assert()'s
     CHECKENABLE useSwitchError = CHECKENABLE._default;  // check for switches without a default
     CHECKENABLE boundscheck    = CHECKENABLE._default;  // state of -boundscheck switch

compiler/src/dmd/globals.h

@@ -245,6 +245,7 @@ struct Param
     CHECKENABLE useIn;             // generate precondition checks
     CHECKENABLE useOut;            // generate postcondition checks
     CHECKENABLE useArrayBounds;    // when to generate code for array bounds checks
+    CHECKENABLE useNullCheck;      // when to generate code for null dereference checks
     CHECKENABLE useAssert;         // when to generate code for assert()'s
     CHECKENABLE useSwitchError;    // check for switches without a default
     CHECKENABLE boundscheck;       // state of -boundscheck switch