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Build clean under -Wall, with -Werror in CI only

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TODO.md item 37 said the cast sweep buys nothing until the build turns on the
warnings those casts suppress. This is that precondition, and the argument
turned out to be right with evidence: -Wall found three genuine signedness
mismatches in sprite.c, where uint32_t width, height and speed were passed
straight to akgl_get_json_integer_value(..., int *). A cast would have silenced
all three. Fixing them properly also turned up that speed is scaled by a million
into a 32-bit field, so anything past 4294 ms overflowed rather than being held.

The other real finding was ten -Wstringop-truncation warnings, every one a
fixed-width strncpy. Those leave a name field unterminated when the input fills
it -- and those fields are registry keys, handed to strcmp and SDL property
calls that do not stop at the field. Same overread class fixed twice already
this release. All ten now use aksl_strncpy from akstdlib, which always
terminates and never NUL-pads, bounded to size - 1 so an over-long name still
truncates rather than being refused. staticstring.h documented the old strncpy
semantics explicitly and has been rewritten to match.

Two sites in game.c are deliberately left on strncpy: both stage into a
pre-zeroed buffer for the savegame's fixed-width fields, where the NUL padding
is part of the format. Neither is flagged.

sprite.c also had a memcpy of a full 128-byte field from a NUL-terminated
string, which reads past the end of any shorter name. Not flagged by anything;
found while converting its neighbours.

-Werror is an option, default OFF, on only in the cmake_build and performance CI
jobs. libakgl is consumed with add_subdirectory -- akbasic does exactly that --
so a target-level -Werror turns every diagnostic a newer compiler invents into a
broken build for somebody else. The warning set is not even stable across build
types here: an -O2 build reports ten warnings that -O0 and -fsyntax-only do not,
because they need the middle end. The two jobs that set it are one of each.

-Wextra is deliberately not adopted. It adds 22 findings, 17 inherent to the
design: 13 -Wunused-parameter from backend vtables and SDL callbacks that must
match a signature, and 4 -Wimplicit-fallthrough from libakerror's own
PROCESS/HANDLE/HANDLE_GROUP, which fall through by design. Filed upstream as
deps/libakerror TODO item 8; the submodule bump carries it.

deps/semver/semver.c is listed directly in add_library, so the target's PRIVATE
options reach it. Exempted with -w so a future semver update cannot fail this
build -- verified by forcing -Wextra -Werror and watching our files fail while
semver compiled clean.

Verified: RelWithDebInfo, Debug and coverage builds all clean under -Werror;
-Werror actually fails on a planted unused variable; an embedded consumer with
AKGL_WERROR unset still configures and builds. 25/25 pass, memcheck clean,
reindent --check, check_api_surface and check_error_protocol clean.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
This commit is contained in:
Andrew Kesterson
2026-08-01 09:18:52 -04:00
parent b899f09fc8
commit 4d80664cd9
16 changed files with 230 additions and 62 deletions
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39
include/akgl/staticstring.h
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@@ -27,16 +27,18 @@ typedef struct
/**
* @brief Set a pooled string's contents and mark the slot in use.
*
* Copies at most #AKGL_MAX_STRING_LENGTH bytes out of @p init, or zeroes the
* buffer when @p init is `NULL`, then sets `refcount` to 1. Callers normally
* reach this through akgl_heap_next_string rather than calling it directly.
* Copies @p init into the buffer, or zeroes it when @p init is `NULL`, then
* sets `refcount` to 1. Callers normally reach this through
* akgl_heap_next_string rather than calling it directly.
*
* @param obj The pooled string to (re)initialize. Required. Its previous
* contents are discarded without inspection.
* @param init Initial contents, NUL-terminated. Optional -- `NULL` zero-fills
* the buffer instead. An @p init longer than
* #AKGL_MAX_STRING_LENGTH is truncated *and left unterminated*,
* because this is `strncpy` semantics, not `strlcpy`.
* the buffer instead. An @p init that does not fit is truncated,
* and the result is **always NUL-terminated**. Until 0.5.0 this was
* `strncpy` at exactly the buffer size, which left an over-long
* string unterminated -- and a pooled string is handed to `strcmp`,
* `realpath` and SDL property calls, none of which stop at 4096.
* @return `NULL` on success, otherwise an error context owned by the caller.
* @throws AKERR_NULLPOINTER If @p obj is `NULL`.
*
@@ -49,26 +51,27 @@ akerr_ErrorContext AKERR_NOIGNORE *akgl_string_initialize(akgl_String *obj, char
/**
* @brief Copy the contents of one pooled string into another.
*
* A bounded `strncpy` between two already-claimed pool slots. It copies bytes
* only: `refcount` is left alone, so @p dest keeps whatever pool state it had.
* A bounded copy between two already-claimed pool slots. It copies bytes only:
* `refcount` is left alone, so @p dest keeps whatever pool state it had.
*
* @param src Source string. Required. Read up to @p count bytes.
* @param dest Destination string. Required. Overwritten in place; the pool
* @param dest Destination string. Required. Overwritten in place; the pool
* slot must already have been claimed.
* @param count Maximum bytes to copy. 0 selects #AKGL_MAX_STRING_LENGTH, the
* whole buffer. A @p count shorter than the source truncates
* without writing a terminator; a @p count longer than the source
* zero-pads the remainder, per `strncpy`. A negative @p count, or
* one above #AKGL_MAX_STRING_LENGTH, is refused -- both buffers
* are exactly that long, so a larger count walked off the end of
* two pool slots at once.
* whole buffer. A @p count shorter than the source truncates, and
* the result is **always NUL-terminated**. The remainder is not
* zero-padded, so this no longer writes the full buffer for a
* short copy. A negative @p count, or one above
* #AKGL_MAX_STRING_LENGTH, is refused -- both buffers are exactly
* that long, so a larger count walked off the end of two pool
* slots at once.
* @return `NULL` on success, otherwise an error context owned by the caller.
* @throws AKERR_NULLPOINTER If @p src or @p dest is `NULL`.
* @throws AKERR_OUTOFBOUNDS If @p count is negative or above
* #AKGL_MAX_STRING_LENGTH.
* @throws errno Whatever `errno` holds if `strncpy` returns something other
* than @p dest. In practice `strncpy` always returns its destination, so
* this path is unreachable rather than merely rare.
* @throws AKERR_VALUE, AKERR_OUTOFBOUNDS Whatever `aksl_strncpy` reports. The
* unreachable `errno` path this used to document went with the
* `strncpy` call it described.
*/
akerr_ErrorContext AKERR_NOIGNORE *akgl_string_copy(akgl_String *src, akgl_String *dest, int count);
#endif //_AKGL_STATICSTRING_H_