xbolva00 added a comment. From post commit discussion, Nico Weber:
1. Hi, 2. 3. this results in a false positive on webrtc, on this code: 4. 5. https://cs.chromium.org/chromium/src/third_party/libwebp/src/enc/picture_csp_enc.c?q=picture_csp_enc.c&sq=package:chromium&dr&l=1002 6. 7. The code does this: 8. 9. #ifdef WORDS_BIGENDIAN 10. #define ALPHA_OFFSET 0 // uint32_t 0xff000000 is 0xff,00,00,00 in memory 11. #else 12. #define ALPHA_OFFSET 3 // uint32_t 0xff000000 is 0x00,00,00,ff in memory 13. #endif 14. 15. // ... 16. 17. const uint8_t* const argb = (const uint8_t*)picture->argb; 18. const uint8_t* const a = argb + (0 ^ ALPHA_OFFSET); 19. const uint8_t* const r = argb + (1 ^ ALPHA_OFFSET); 20. const uint8_t* const g = argb + (2 ^ ALPHA_OFFSET); 21. const uint8_t* const b = argb + (3 ^ ALPHA_OFFSET); 22. 23. The idea is to get bytes 0, 1, 2, 3 as a, r, g, b if ALPHA_OFFSET is 0, or bytes 3, 2, 1, 0 if ALPHA_OFFSET is 3. 24. 25. Maybe this shouldn't fire if the rhs is a macro? 26. 27. (On all of Chromium, this fired 3 times; in the other 2 cases the rhs was a literal as well, and those two were true positives.) Repository: rC Clang CHANGES SINCE LAST ACTION https://reviews.llvm.org/D66397/new/ https://reviews.llvm.org/D66397 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
