path: root/sha1dc
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authorJunio C Hamano <>2017-03-25 17:05:13 (GMT)
committerJunio C Hamano <>2017-03-26 22:34:44 (GMT)
commit7e71542e8b79ddd5164bf3ac5f11cae3b7d006ab (patch)
tree2527eb99ab6e4c2bb219bab1fefc62f690d914ef /sha1dc
parente6b07da2780f349c29809bd75d3eca6ad3c35d19 (diff)
sha1dc: avoid CPP macro collisions
In an early part of sha1dc/sha1.c, the code checks the endianness of the target platform by inspecting common CPP macros defined on big-endian boxes, and sets BIGENDIAN macro to 1. If these common CPP macros are not defined, the code declares that the target platform is little endian and does nothing (most notably, it does not #undef its BIGENDIAN macro). The code that does so even has this comment Note that all MSFT platforms are little endian, so none of these will be defined under the MSC compiler. and later, the defined-ness of the BIGENDIAN macro is used to switch the implementation of sha1_load() macro. One thing the code did not anticipate is that somebody might define BIGENDIAN macro in some header it includes to 0 on a little-endian target platform. Because the auto-detection based on common macros do not touch BIGENDIAN macro when it detects a little-endian target, such a definition is still valid and then defined-ness test will say "Ah, BIGENDIAN is defined" and takes the wrong sha1_load(). As this auto-detection logic pretends as if it owns the BIGENDIAN macro by ignoring the setting that may come from the outside and by not explicitly unsetting when it decides that it is working for a little-endian target, solve this problem without breaking that assumption. Namely, we can rename BIGENDIAN this code uses to something much less generic, i.e. SHA1DC_BIGENDIAN. For extra protection, undef the macro on a little-endian target. It is possible to work it around by instead #undef BIGENDIAN in the auto-detection code, but a macro (or include) that happens later in the code can be implemented in terms of BIGENDIAN on Windows and it is possible that the implementation gets upset when it sees the CPP macro undef'ed (instead of set to 0). Renaming the private macro intended to be used only in this file to a less generic name relieves us from having to worry about that kind of breakage. Noticed-by: Johannes Schindelin <> Signed-off-by: Junio C Hamano <>
Diffstat (limited to 'sha1dc')
1 files changed, 6 insertions, 5 deletions
diff --git a/sha1dc/sha1.c b/sha1dc/sha1.c
index 6dd0da3..35e9dd5 100644
--- a/sha1dc/sha1.c
+++ b/sha1dc/sha1.c
@@ -12,7 +12,7 @@
Because Little-Endian architectures are most common,
- we only set BIGENDIAN if one of these conditions is met.
+ we only set SHA1DC_BIGENDIAN if one of these conditions is met.
Note that all MSFT platforms are little endian,
so none of these will be defined under the MSC compiler.
If you are compiling on a big endian platform and your compiler does not define one of these,
@@ -23,8 +23,9 @@
defined(__BIG_ENDIAN__) || defined(__ARMEB__) || defined(__THUMBEB__) || defined(__AARCH64EB__) || \
defined(_MIPSEB) || defined(__MIPSEB) || defined(__MIPSEB__)
-#define BIGENDIAN (1)
#define rotate_right(x,n) (((x)>>(n))|((x)<<(32-(n))))
@@ -35,11 +36,11 @@
#define sha1_mix(W, t) (rotate_left(W[t - 3] ^ W[t - 8] ^ W[t - 14] ^ W[t - 16], 1))
-#if defined(BIGENDIAN)
+#if defined(SHA1DC_BIGENDIAN)
#define sha1_load(m, t, temp) { temp = m[t]; }
#define sha1_load(m, t, temp) { temp = m[t]; sha1_bswap32(temp); }
-#endif /*define(BIGENDIAN)*/
+#endif /* !defined(SHA1DC_BIGENDIAN) */
#define sha1_store(W, t, x) *(volatile uint32_t *)&W[t] = x