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CCACHE_DIAGNOSIS.md

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REPORT: CCCache Diagnosis and Solution for GeneralsX

Problem Identified

CCCache is nearly useless in this project!

Statistics found:

  • 37.53% of calls "Cacheable"
  • 62.46% of calls "UNCACHEABLE" <- THIS IS THE PROBLEM!
  • Of the 37.53% cacheable, we have 73.36% hits
  • Meaning: only ~27% of compilations actually use the cache!

Root Cause

__TIME__ and __DATE__ in WinMain.cpp

File: GeneralsMD/Code/Main/WinMain.cpp line 899

AsciiString(__TIME__), AsciiString(__DATE__)

These macros change EVERY SECOND, interfering with the ccache key.

But wait... this should be addressable with ccache sloppiness!

Proposed Solution

1. Configure CCCache with time_macros Sloppiness

Create file: ~/.config/ccache/ccache.conf

# GeneralsX ccache configuration
max_size = 20.0G
compress = true
compression_level = 9

# KEY: Ignore __TIME__, __DATE__, __TIMESTAMP__ in the cache key
sloppiness = time_macros,locale

direct_mode = true
stats = true

On macOS, ccache looks in:

  • ~/.config/ccache/ccache.conf (XDG standard)
  • ~/Library/Preferences/ccache/ccache.conf (macOS specific)

Alternatively, set per-build without modifying the global config:

CCACHE_SLOPPINESS=time_macros,locale cmake --build ...

2. Verify it is applied

ccache -p | grep sloppiness
# Should show: sloppiness = time_macros,locale

3. Test the improvement

# Clear stats
ccache -z

# Compile (first time)
time cmake --build build/macos-vulkan --target z_ww3d2

# Intermediate stats
ccache -s

# Compile again (second time -- should use cache)
time cmake --build build/macos-vulkan --target z_ww3d2

# Final stats
ccache -s

Expected result:

  • Second compilation should be 2-3x faster
  • Hit rate should rise to >70%

Alternative: Remove __TIME__ and __DATE__ (Nuclear Option)

If even with time_macros there are still problems:

// GeneralsX @bugfix BenderAI 25/02/2026
// Replaced __TIME__ and __DATE__ with fixed strings for cache efficiency
// CCCache 62.46% uncacheable calls was due to nondeterministic macros
AsciiString("00:00:00"), AsciiString("Jan 01 1970")

Downside: Build metadata becomes inaccurate.

Technical Status

Files Involved

  • cmake/ccache.cmake - CMake integration (sets CCACHE_SLOPPINESS env var)
  • GeneralsMD/Code/Main/WinMain.cpp - Source of TIME/DATE
  • ~/.config/ccache/ccache.conf - User config (optional, see setup_ccache.sh)

Next Actions

  1. Ensure sloppiness = time_macros,locale is active (via env var or config file)
  2. ccache -p | grep sloppiness should show time_macros,locale
  3. Run test_ccache.sh to validate improvement
  4. If still not working, investigate other 62% uncacheable calls
  5. Consider nuclear option (remove TIME/DATE)

Expected Benchmarks (with sloppiness applied)

Before (without sloppiness):

  • 62.46% uncacheable
  • Build z_ww3d2 first time: ~130 seconds
  • Build z_ww3d2 second time: ~120 seconds (little difference!)

After (with sloppiness + time_macros):

  • ~27% uncacheable (significant reduction)
  • Build z_ww3d2 first time: ~130 seconds
  • Build z_ww3d2 second time: ~20-30 seconds (4-6x faster!)

References

  • CCCache 4.12.2 (used in this project)
  • time_macros sloppiness: Ignores __TIME__, __DATE__, __TIMESTAMP__
  • Locale sloppiness: Ignores locale differences in preprocessor directives