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GCC13_BUILD_FIXES.md

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Movian Build Fixes for GCC 13.3.0

This document describes the compilation fixes applied to build Movian successfully with GCC 13.3.0 on Ubuntu 24.04.

Context

Movian (formerly Showtime) is a media player application that hadn't been updated for modern GCC versions. When attempting to build with GCC 13.3.0, numerous compilation errors occurred due to:

  • Stricter compiler warnings treated as errors (-Werror)
  • Changes in GCC's handling of attributes and warnings
  • Improved static analysis detecting potential issues
  • Deprecation of older OpenSSL APIs

Fixes Applied

1. libav Inline Assembly Compatibility

File: configure.linux Change: Added --disable-inline-asm to LIBAV_ARCH_FLAGS

LIBAV_ARCH_FLAGS="--disable-shared --enable-static --disable-inline-asm"

Reason: GCC 13.3.0's assembler is stricter about operand types in inline assembly. The libav library (FFmpeg fork) contains x86-specific inline assembly that uses shr (shift right) operations with incompatible operand types. Disabling inline assembly forces libav to use C implementations instead.

2. VMIR Function Return Type

File: ext/vmir/src/vmir.c Change: Changed vmir_load function signature

vmir_errcode_t vmir_load(ir_unit_t *iu, const uint8_t *u8, int len)

Reason: The function was declared to return vmir_errcode_t (an enum) but implemented to return int. GCC 13.3.0 is stricter about type mismatches.

3. File Stream Management

Files: src/arch/linux/linux_main.c, src/arch/posix/posix.c Change: Replaced fclose() with pclose() for popen() streams

pclose(fp);  // instead of fclose(fp);

Reason: GCC 13.3.0 includes a new warning -Wmismatched-dealloc that detects when the wrong deallocation function is used. popen() streams must be closed with pclose(), not fclose().

4. alloc_size Attribute Warning

File: Makefile Change: Added specific CFLAGS rule for linux_misc.o

${BUILDDIR}/src/arch/linux/linux_misc.o : CFLAGS = ${CFLAGS_std} ${OPTFLAGS} -Wno-error=attributes

Reason: The libav header libavutil/mem.h uses the alloc_size attribute on a function returning int, but this attribute is meant for functions returning pointers. GCC 13.3.0 treats this as an error with -Werror=attributes.

5. NULL Format String Arguments

Files: src/backend/bittorrent/tracker_udp.c, src/backend/icecast/icecast.c, src/ui/glw/glw_texture_loader.c Change: Added null checks for rstr_get() calls

TRACE(TRACE_DEBUG, "Tag", "Value: %s", rstr_get(str) ? rstr_get(str) : "(null)")

Reason: GCC 13.3.0's -Wformat-overflow= warning detects when NULL pointers might be passed to %s format specifiers. The rstr_get() function can return NULL.

6. Redundant NULL Check on Static Array

File: src/i18n.c Change: Removed unnecessary NULL check

// Before
if(vec[i] && !strcasecmp(vec[i], str))

// After
if(!strcasecmp(vec[i], str))

Reason: vec is a static 2D array parameter, so vec[i] can never be NULL. GCC 13.3.0's -Waddress warning detects this always-true comparison.

7. Use-After-Free in realloc

File: src/ui/glw/glw_renderer.c Change: Restructured pointer adjustment logic

// Save offsets before realloc
ptrdiff_t *offsets = malloc(old_capacity * sizeof(ptrdiff_t));
for(int i = 0; i < old_capacity; i++) {
  offsets[i] = gr->gr_render_order[i].job - gr->gr_render_jobs;
}

// After realloc
for(int i = 0; i < old_capacity; i++) {
  gr->gr_render_order[i].job = gr->gr_render_jobs + offsets[i];
}

Reason: GCC 13.3.0's -Wuse-after-free warning detects potential use of invalidated pointers after realloc(). The original code used the old pointer in arithmetic after realloc might have moved the memory.

GCC 13.3.0 Impact

GCC 13.3.0 introduced several new warnings and stricter enforcement:

  • -Wattributes: Now errors on incorrect attribute usage
  • -Wmismatched-dealloc: Detects wrong deallocation functions
  • -Wformat-overflow=: Stricter format string checking
  • -Waddress: Detects always-true pointer comparisons
  • -Wuse-after-free: Better detection of use-after-free patterns

Combined with Movian's use of -Werror, these became compilation failures.

Build Instructions

After applying these fixes:

./configure.linux
make

The resulting binary will be at build.linux/movian.

Notes

  • These fixes maintain backward compatibility with older GCC versions
  • No functional changes were made, only compilation warnings/errors were addressed
  • The libav inline assembly disable may have minor performance impact but ensures compatibility
  • All fixes follow the principle of minimal, targeted changes /home/roman/Code/movian/GCC13_BUILD_FIXES.md