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  • Cheng Shao's avatar
    83341bbc
    rts: use __builtin_offsetof to implement STG_FIELD_OFFSET · 83341bbc
    Cheng Shao authored and Ben Gamari's avatar Ben Gamari committed 
    This patch fixes the STG_FIELD_OFFSET macro definition by using
__builtin_offsetof, which is what gcc/clang uses to implement offsetof
in standard C. The previous definition that uses NULL pointer involves
subtle undefined behavior in C and thus reported by
UndefinedBehaviorSanitizer as well:

```
rts/Capability.h:243:58: runtime error: member access within null pointer of type 'Capability' (aka 'struct Capability_')
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior rts/Capability.h:243:58
```
    83341bbc
    rts: use __builtin_offsetof to implement STG_FIELD_OFFSET
    Cheng Shao authored and Ben Gamari's avatar Ben Gamari committed 
    This patch fixes the STG_FIELD_OFFSET macro definition by using
__builtin_offsetof, which is what gcc/clang uses to implement offsetof
in standard C. The previous definition that uses NULL pointer involves
subtle undefined behavior in C and thus reported by
UndefinedBehaviorSanitizer as well:

```
rts/Capability.h:243:58: runtime error: member access within null pointer of type 'Capability' (aka 'struct Capability_')
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior rts/Capability.h:243:58
```