From 6a1cefac196f45d766027c97a6c8c44459c9cccd Mon Sep 17 00:00:00 2001 From: Joseph Myers Date: Wed, 11 Jan 2017 15:28:08 +0000 Subject: Make endian-conversion macros always return correct types (bug 16458). Bug 16458 reports that the endian-conversion macros in and , in the case where no endian conversion is needed, just return their arguments without converting to the expected return type, so failing to act as expected for a macro version of a function. (The macros, in particular, are described with prototypes in POSIX so should act like correspondingly prototyped functions.) Where previously this was a fairly obscure issue, it now results in glibc build with GCC mainline breaking for big-endian systems: nss_hesiod/hesiod-service.c: In function '_nss_hesiod_getservbyport_r': nss_hesiod/hesiod-service.c:142:39: error: '%d' directive output may be truncated writing between 1 and 11 bytes into a region of size 6 [-Werror=format-truncation=] snprintf (portstr, sizeof portstr, "%d", ntohs (port)); ^~ nss_hesiod/hesiod-service.c:142:38: note: using the range [1, -2147483648] for directive argument snprintf (portstr, sizeof portstr, "%d", ntohs (port)); ^~~~ nss_hesiod/hesiod-service.c:142:3: note: format output between 2 and 12 bytes into a destination of size 6 snprintf (portstr, sizeof portstr, "%d", ntohs (port)); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The port argument is passed as int to this function, so when ntohs does not convert the compiler cannot tell that the result is within the range of uint16_t. (I don't know if in fact it's possible for out-of-range values to reach this function and so get truncated as strings without this patch or as integers with it.) This patch arranges for these macros to use identity functions to ensure appropriate conversions while having warnings for implicit conversions of function arguments that might not occur with a cast. Tested for x86_64 and x86; with build-many-glibcs.py with GCC 6; and with build-many-glibcs.py with GCC mainline for powerpc to test the build fix. [BZ #16458] * bits/uintn-identity.h: New file. * inet/netinet/in.h: Include . [__BYTE_ORDER == __BIG_ENDIAN] (ntohl): Use __uint32_identity. [__BYTE_ORDER == __BIG_ENDIAN] (ntohs): Use __uint16_identity. [__BYTE_ORDER == __BIG_ENDIAN] (htonl): Use __uint32_identity. [__BYTE_ORDER == __BIG_ENDIAN] (htohs): Use __uint16_identity. * string/endian.h: Include . [__BYTE_ORDER == __LITTLE_ENDIAN] (htole16): Use __uint16_identity. [__BYTE_ORDER == __LITTLE_ENDIAN] (le16toh): Likewise. [__BYTE_ORDER == __LITTLE_ENDIAN] (htole32): Use __uint32_identity. [__BYTE_ORDER == __LITTLE_ENDIAN] (le32toh): Likewise. [__BYTE_ORDER == __LITTLE_ENDIAN] (htole64): Use __uint64_identity. [__BYTE_ORDER == __LITTLE_ENDIAN] (le64toh): Likewise. [__BYTE_ORDER != __LITTLE_ENDIAN] (htobe16): Use __uint16_identity. [__BYTE_ORDER != __LITTLE_ENDIAN] (be16toh): Likewise. [__BYTE_ORDER != __LITTLE_ENDIAN] (htobe32): Use __uint32_identity. [__BYTE_ORDER != __LITTLE_ENDIAN] (be32toh): Likewise. [__BYTE_ORDER != __LITTLE_ENDIAN] (htobe64): Use __uint64_identity. [__BYTE_ORDER != __LITTLE_ENDIAN] (be64toh): Likewise. * string/Makefile (headers): Add bits/uintn-identity.h. (tests): Add test-endian-types. * string/test-endian-types.c: New file. * inet/Makefile (tests): Add test-hnto-types. * inet/test-hnto-types.c: New file. --- inet/netinet/in.h | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) (limited to 'inet/netinet') diff --git a/inet/netinet/in.h b/inet/netinet/in.h index 419e119172..365bc6878e 100644 --- a/inet/netinet/in.h +++ b/inet/netinet/in.h @@ -383,6 +383,7 @@ extern uint16_t htons (uint16_t __hostshort) /* Get machine dependent optimized versions of byte swapping functions. */ #include +#include #ifdef __OPTIMIZE__ /* We can optimize calls to the conversion functions. Either nothing has @@ -391,10 +392,10 @@ extern uint16_t htons (uint16_t __hostshort) # if __BYTE_ORDER == __BIG_ENDIAN /* The host byte order is the same as network byte order, so these functions are all just identity. */ -# define ntohl(x) (x) -# define ntohs(x) (x) -# define htonl(x) (x) -# define htons(x) (x) +# define ntohl(x) __uint32_identity (x) +# define ntohs(x) __uint16_identity (x) +# define htonl(x) __uint32_identity (x) +# define htons(x) __uint16_identity (x) # else # if __BYTE_ORDER == __LITTLE_ENDIAN # define ntohl(x) __bswap_32 (x) -- cgit 1.4.1