From 8eeb9da6d017761037bf757780ea544dfeabbad8 Mon Sep 17 00:00:00 2001 From: Mike Frysinger Date: Tue, 31 Jul 2012 09:02:35 +0000 Subject: libiberty/md5: fix strict alias warnings MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Current libiberty md5 code triggers these warnings with gcc-4.7.1 for me: libiberty/md5.c: In function ‘md5_finish_ctx’: libiberty/md5.c:117:3: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing] libiberty/md5.c:118:3: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing] The change below fixes things for me. The optimized output (-O2) is the same before/after my change on x86_64-linux. I imagine it'll be the same for most targets. It seems simpler than using a union on the md5_ctx buffer since these are the only two locations in the code where this occurs. --- libiberty/ChangeLog | 5 +++++ libiberty/md5.c | 12 ++++++++---- 2 files changed, 13 insertions(+), 4 deletions(-) (limited to 'libiberty') diff --git a/libiberty/ChangeLog b/libiberty/ChangeLog index 349dc98eb06..6615047ad25 100644 --- a/libiberty/ChangeLog +++ b/libiberty/ChangeLog @@ -1,3 +1,8 @@ +2012-07-31 Mike Frysinger + + * md5.c (md5_finish_ctx): Declare swap_bytes. Assign SWAP() output + to swap_bytes, and then call memcpy to move it to ctx->buffer. + 2012-07-26 Kazu Hirata Sandra Loosemore diff --git a/libiberty/md5.c b/libiberty/md5.c index 0db8fc8936f..8cc0cb5fe96 100644 --- a/libiberty/md5.c +++ b/libiberty/md5.c @@ -103,6 +103,7 @@ md5_finish_ctx (struct md5_ctx *ctx, void *resbuf) { /* Take yet unprocessed bytes into account. */ md5_uint32 bytes = ctx->buflen; + md5_uint32 swap_bytes; size_t pad; /* Now count remaining bytes. */ @@ -113,10 +114,13 @@ md5_finish_ctx (struct md5_ctx *ctx, void *resbuf) pad = bytes >= 56 ? 64 + 56 - bytes : 56 - bytes; memcpy (&ctx->buffer[bytes], fillbuf, pad); - /* Put the 64-bit file length in *bits* at the end of the buffer. */ - *(md5_uint32 *) &ctx->buffer[bytes + pad] = SWAP (ctx->total[0] << 3); - *(md5_uint32 *) &ctx->buffer[bytes + pad + 4] = SWAP ((ctx->total[1] << 3) | - (ctx->total[0] >> 29)); + /* Put the 64-bit file length in *bits* at the end of the buffer. + Use memcpy to avoid aliasing problems. On most systems, this + will be optimized away to the same code. */ + swap_bytes = SWAP (ctx->total[0] << 3); + memcpy (&ctx->buffer[bytes + pad], &swap_bytes, sizeof (swap_bytes)); + swap_bytes = SWAP ((ctx->total[1] << 3) | (ctx->total[0] >> 29)); + memcpy (&ctx->buffer[bytes + pad + 4], &swap_bytes, sizeof (swap_bytes)); /* Process last bytes. */ md5_process_block (ctx->buffer, bytes + pad + 8, ctx); -- cgit v1.2.1