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| author | Alan Modra <amodra@gmail.com> | 2021-05-15 14:36:26 +0930 |
|---|---|---|
| committer | Alan Modra <amodra@gmail.com> | 2021-05-15 14:36:54 +0930 |
| commit | fc5e0925d4bff79c8c036cf00803112a1ec04188 (patch) | |
| tree | d71d622247fdaadaa710ece3fdce8bfb9ffc2289 /binutils/bucomm.h | |
| parent | 7c96e6120f1b9b5025629bbe995ca55d1be8f36f (diff) | |
| download | gdb-fc5e0925d4bff79c8c036cf00803112a1ec04188.zip gdb-fc5e0925d4bff79c8c036cf00803112a1ec04188.tar.gz gdb-fc5e0925d4bff79c8c036cf00803112a1ec04188.tar.bz2 | |
_mul_overflow and get_encoded_value
A sufficiently mad compiler optimiser can take undefined behaviour
according to the C standard as an opportunity to remove code. Since
"data + size" might be seen to be past the end of an array,
calculating such an expression is UB.
_mul_overflow is infrastructure for later patches.
* bucomm.h (_mul_overflow): Define.
* dwarf.c (get_encoded_value): Avoid pointer UB.
Diffstat (limited to 'binutils/bucomm.h')
| -rw-r--r-- | binutils/bucomm.h | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/binutils/bucomm.h b/binutils/bucomm.h index 78f6176..2769c27 100644 --- a/binutils/bucomm.h +++ b/binutils/bucomm.h @@ -80,4 +80,12 @@ void *xmalloc (size_t); void *xrealloc (void *, size_t); +#if __GNUC__ >= 7 +#define _mul_overflow(a, b, res) __builtin_mul_overflow (a, b, res) +#else +/* Assumes unsigned values. Careful! Args evaluated multiple times. */ +#define _mul_overflow(a, b, res) \ + ((*res) = (a), (*res) *= (b), (b) != 0 && (*res) / (b) != (a)) +#endif + #endif /* _BUCOMM_H */ |