stdlib format improvements - #11502
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indentation_bin/5 used N as an absolute byte offset but passed it to binary:part/3 as a segment length. This caused a badarg crash when a binary containing a tab was passed to indentation/2, which happens via fwrite_bin when ~ts precedes ~p. Additionally, the newline clause reset N to 0 without updating Start, causing wrong indentation after multiple newlines. Fix by making N relative to Start (i.e. the segment length).
A negative precision passed via ~.* (e.g. io_lib:format("~.*c", [-1, $a]))
would cause infinite recursion in chars/2 since -1 bsr 1 = -1.
Other controls (~.*f, ~.*s, etc.) would crash with function_clause.
Fix by validating precision >= 0 in precision/2, raising badarg
consistently for all controls. This matches C printf semantics
where negative precision via * is defined behavior (treated as
omitted), but Erlang chooses to reject it explicitly.
The latin1 list clause in flat_trunc/3 used lists:flatten + lists:split which materializes the entire input (O(L)) just to take N chars. Replace with string:slice/3 which is O(N), matching the existing unicode clause. Also merge both list clauses into one since string:slice handles both encodings.
The ?IND macro called list_to_binary(Ind) on every line wrap in the binary pretty-printer loops (pp_tail_bin, pp_pairs_tail_bin, pp_fields_tail_bin, pp_binary_bin_ind). Since Ind is constant within each loop, this re-flattened the same iolist on every sibling element that wrapped to a new line. Fix by converting Ind to binary lazily only in the branch that actually wraps, then threading the binary through subsequent iterations. The ?IND macro now expects a binary argument directly.
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string_bin_escape_unicode/6 passed all bytes > 127 through without checking for C1 control characters (U+0080-U+009F). These encode as 0xC2 0x80-0x9F in UTF-8 and could enable terminal control injection when rendering untrusted strings. Fix by matching the specific two-byte C1 sequences and octal-escaping them, consistent with the list-based write_string path.
Previously, chars_limit only capped the field width for ~s via limit_field/2. Other controls (~c, ~n, ~~, ~w, ~W, ~e, ~f, etc.) could allocate unbounded padding that bypassed chars_limit entirely. Fix by passing chars_limit to build_small/build_small_bin and applying limit_field to the field width before calling control_small. Also apply limit_field in control_limited for ~w/~W. Without chars_limit set, behavior is unchanged.
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Fixes AI findings.
Use OTP-20232.