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Migrate feature detection macro checks from #ifdef to #if.

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The #if predicate evaluates to false if the macro is undefined, or
defined to 0. #ifdef (and its synonym #if defined) evaluates to false
only if the macro is undefined.

The new setup allows differentiating between setting a macro to 0 (to
express that the capability definitely does not exist / should not be
used) and leaving a macro undefined (to express not knowing whether a
capability exists / not caring if a capability is used).

PiperOrigin-RevId: 391094241
This commit is contained in:
Victor Costan
2021-08-16 18:22:31 +00:00
committed by Victor Costan
parent a8400f1fab
commit cbb83a1d64
7 changed files with 44 additions and 43 deletions
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24
snappy-stubs-internal.h
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@@ -31,7 +31,7 @@
#ifndef THIRD_PARTY_SNAPPY_OPENSOURCE_SNAPPY_STUBS_INTERNAL_H_
#define THIRD_PARTY_SNAPPY_OPENSOURCE_SNAPPY_STUBS_INTERNAL_H_
#ifdef HAVE_CONFIG_H
#if HAVE_CONFIG_H
#include "config.h"
#endif
@@ -43,11 +43,11 @@
#include <limits>
#include <string>
#ifdef HAVE_SYS_MMAN_H
#if HAVE_SYS_MMAN_H
#include <sys/mman.h>
#endif
#ifdef HAVE_UNISTD_H
#if HAVE_UNISTD_H
#include <unistd.h>
#endif
@@ -90,20 +90,20 @@
#define ARRAYSIZE(a) int{sizeof(a) / sizeof(*(a))}
// Static prediction hints.
#ifdef HAVE_BUILTIN_EXPECT
#if HAVE_BUILTIN_EXPECT
#define SNAPPY_PREDICT_FALSE(x) (__builtin_expect(x, 0))
#define SNAPPY_PREDICT_TRUE(x) (__builtin_expect(!!(x), 1))
#else
#define SNAPPY_PREDICT_FALSE(x) x
#define SNAPPY_PREDICT_TRUE(x) x
#endif
#endif // HAVE_BUILTIN_EXPECT
// Inlining hints.
#ifdef HAVE_ATTRIBUTE_ALWAYS_INLINE
#if HAVE_ATTRIBUTE_ALWAYS_INLINE
#define SNAPPY_ATTRIBUTE_ALWAYS_INLINE __attribute__((always_inline))
#else
#define SNAPPY_ATTRIBUTE_ALWAYS_INLINE
#endif
#endif // HAVE_ATTRIBUTE_ALWAYS_INLINE
// Stubbed version of ABSL_FLAG.
//
@@ -235,11 +235,11 @@ class LittleEndian {
}
static inline constexpr bool IsLittleEndian() {
#if defined(SNAPPY_IS_BIG_ENDIAN)
#if SNAPPY_IS_BIG_ENDIAN
return false;
#else
return true;
#endif // defined(SNAPPY_IS_BIG_ENDIAN)
#endif // SNAPPY_IS_BIG_ENDIAN
}
};
@@ -265,7 +265,7 @@ class Bits {
void operator=(const Bits&);
};
#if defined(HAVE_BUILTIN_CTZ)
#if HAVE_BUILTIN_CTZ
inline int Bits::Log2FloorNonZero(uint32_t n) {
assert(n != 0);
@@ -354,7 +354,7 @@ inline int Bits::FindLSBSetNonZero(uint32_t n) {
#endif // End portable versions.
#if defined(HAVE_BUILTIN_CTZ)
#if HAVE_BUILTIN_CTZ
inline int Bits::FindLSBSetNonZero64(uint64_t n) {
assert(n != 0);
@@ -388,7 +388,7 @@ inline int Bits::FindLSBSetNonZero64(uint64_t n) {
}
}
#endif // End portable version.
#endif // HAVE_BUILTIN_CTZ
// Variable-length integer encoding.
class Varint {