For memeq and friends, "tor_" indicates constant-time and "fast_"
indicates optimized. I'm fine with leaving the constant-time
"safe_mem_is_zero" with its current name, but the "tor_" prefix on
the current optimized version is misleading.
Also, make the tor_digest*_is_zero() uniformly constant-time, and
add a fast_digest*_is_zero() version to use as needed.
A later commit in this branch will fix all the users of
tor_mem_is_zero().
Closes ticket 30309.
When we do redefine them, use inline functions instead of #define.
This fixes a latent code problem in our redefinition of these
functions, which was exposed by our refactoring: Previously, we
would #define strcasecmp after string.h was included, so nothing bad
would happen. But when we refactored, we would sometimes #define it
first, which was a problem on mingw, whose headers contain
(approximately):
inline int strcasecmp (const char *a, const char *b)
{ return _stricmp(a,b); }
Our define turned this into:
inline int _stricmp(const char *a, const char *b)
{ return _stricmp(a,b); }
And GCC would correctly infer that this function would loop forever,
rather than actually comparing anything. This caused bug 26594.
Fixes bug 26594; bug not in any released version of Tor.
