3 ms·

In GNU C one can add the statement asm ("" : : "m" (&key)); just before or after the memset, effectively telling the compiler that the address of "key" es

• fafner 12y ago
  GCC also has an `optimize' function attribute which might make sense to use here. This can set optimizations for the function to -O0. But I haven't tried it.
  • cesarb 12y ago
    That's not enough, since even -O0 applies a few optimizations, and which optimizations it applies could change in the future. The best answer is really GCC's __asm__("" : : "m" (&key)), or perhaps something like __asm__("" : : "r" (key) : "memory"), after the memset. It generates no extra code, just ensures that the memset won't be removed. For other compilers (in practice only MSVC, since clang is gcc-compatible), you could pass the pointer to a dummy assembly function instead of using inline assembly; even link-time optimization can't know what happens within a function written in assembly. Or, for better performance, create in assembly a "safer_memset" which is a single instruction: a jump to the real memset function.
• syncsynchalt 12y ago
  That's not portable, whereas the "volatile" solution is.