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ofp-actions: Make struct ofpact constant size across implementations.

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Before commit c2d936a44f (ofp-actions: Centralize all OpenFlow action
code for maintainability.), struct ofpact was 4 bytes with GCC and Clang,
and 12 bytes with other compilers.  That commit changed struct ofpact so
that it remained 4 bytes with GCC and Clang but shrank to 8 bytes on other
compilers.  An unexpected side effect of that change was that the size
of the pad[] array in struct ofpact_nest shrank to 0 bytes, because that
array padded to a multiple of 8 bytes.  MSVC does not support 0-element
arrays, so this caused a build failure.

This commit fixes the problem by changing struct ofpact so that it is 4
bytes with every compiler.

Reported-by: Alin Serdean <aserdean@cloudbasesolutions.com>
Signed-off-by: Ben Pfaff <blp@nicira.com>
Acked-by: Alin Serdean <aserdean@cloudbasesolutions.com>
This commit is contained in:
Ben Pfaff
2014-08-12 11:42:56 -07:00
parent e0a42ae29a
commit 80a73e7196
2 changed files with 9 additions and 4 deletions
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1
lib/compiler.h
View File

@@ -169,6 +169,7 @@
* or otherwise exposed outside of a single process. */ * or otherwise exposed outside of a single process. */
#if __GNUC__ && !__CHECKER__ #if __GNUC__ && !__CHECKER__
#define OVS_PACKED_ENUM __attribute__((__packed__)) #define OVS_PACKED_ENUM __attribute__((__packed__))
#define HAVE_PACKED_ENUM
#else #else
#define OVS_PACKED_ENUM #define OVS_PACKED_ENUM
#endif #endif

12
lib/ofp-actions.h
View File

@@ -157,16 +157,20 @@ enum {
* code to translate the ofpact to OpenFlow must tolerate this case.) * code to translate the ofpact to OpenFlow must tolerate this case.)
*/ */
struct ofpact { struct ofpact {
/* We want the space advantage of an 8-bit type here on every
* implementation, without giving up the advantage of having a useful type
* on implementations that support packed enums. */
#ifdef HAVE_PACKED_ENUM
enum ofpact_type type; /* OFPACT_*. */ enum ofpact_type type; /* OFPACT_*. */
#else
uint8_t type; /* OFPACT_* */
#endif
uint8_t raw; /* Original type when added, if any. */ uint8_t raw; /* Original type when added, if any. */
uint16_t len; /* Length of the action, in bytes, including uint16_t len; /* Length of the action, in bytes, including
* struct ofpact, excluding padding. */ * struct ofpact, excluding padding. */
}; };
#ifdef __GNUC__
/* Make sure that OVS_PACKED_ENUM really worked. */
BUILD_ASSERT_DECL(sizeof(struct ofpact) == 4); BUILD_ASSERT_DECL(sizeof(struct ofpact) == 4);
#endif
/* Alignment. */ /* Alignment. */
#define OFPACT_ALIGNTO 8 #define OFPACT_ALIGNTO 8