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

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

7 files changed, 44 insertions, 43 deletions

diff --git a/cmake/config.h.in b/cmake/config.h.in
index 872bd3c..306c7e2 100644
--- a/cmake/config.h.in
+++ b/cmake/config.h.in
@@ -2,46 +2,46 @@
 #define THIRD_PARTY_SNAPPY_OPENSOURCE_CMAKE_CONFIG_H_
 
 /* Define to 1 if the compiler supports __attribute__((always_inline)). */
-#cmakedefine HAVE_ATTRIBUTE_ALWAYS_INLINE 1
+#cmakedefine01 HAVE_ATTRIBUTE_ALWAYS_INLINE
 
 /* Define to 1 if the compiler supports __builtin_ctz and friends. */
-#cmakedefine HAVE_BUILTIN_CTZ 1
+#cmakedefine01 HAVE_BUILTIN_CTZ
 
 /* Define to 1 if the compiler supports __builtin_expect. */
-#cmakedefine HAVE_BUILTIN_EXPECT 1
+#cmakedefine01 HAVE_BUILTIN_EXPECT
 
 /* Define to 1 if you have a definition for mmap() in <sys/mman.h>. */
-#cmakedefine HAVE_FUNC_MMAP 1
+#cmakedefine01 HAVE_FUNC_MMAP
 
 /* Define to 1 if you have a definition for sysconf() in <unistd.h>. */
-#cmakedefine HAVE_FUNC_SYSCONF 1
+#cmakedefine01 HAVE_FUNC_SYSCONF
 
 /* Define to 1 if you have the `lzo2' library (-llzo2). */
-#cmakedefine HAVE_LIBLZO2 1
+#cmakedefine01 HAVE_LIBLZO2
 
 /* Define to 1 if you have the `z' library (-lz). */
-#cmakedefine HAVE_LIBZ 1
+#cmakedefine01 HAVE_LIBZ
 
 /* Define to 1 if you have the `lz4' library (-llz4). */
-#cmakedefine HAVE_LIBLZ4 1
+#cmakedefine01 HAVE_LIBLZ4
 
 /* Define to 1 if you have the <sys/mman.h> header file. */
-#cmakedefine HAVE_SYS_MMAN_H 1
+#cmakedefine01 HAVE_SYS_MMAN_H
 
 /* Define to 1 if you have the <sys/resource.h> header file. */
-#cmakedefine HAVE_SYS_RESOURCE_H 1
+#cmakedefine01 HAVE_SYS_RESOURCE_H
 
 /* Define to 1 if you have the <sys/time.h> header file. */
-#cmakedefine HAVE_SYS_TIME_H 1
+#cmakedefine01 HAVE_SYS_TIME_H
 
 /* Define to 1 if you have the <sys/uio.h> header file. */
-#cmakedefine HAVE_SYS_UIO_H 1
+#cmakedefine01 HAVE_SYS_UIO_H
 
 /* Define to 1 if you have the <unistd.h> header file. */
-#cmakedefine HAVE_UNISTD_H 1
+#cmakedefine01 HAVE_UNISTD_H
 
 /* Define to 1 if you have the <windows.h> header file. */
-#cmakedefine HAVE_WINDOWS_H 1
+#cmakedefine01 HAVE_WINDOWS_H
 
 /* Define to 1 if you target processors with SSSE3+ and have <tmmintrin.h>. */
 #cmakedefine01 SNAPPY_HAVE_SSSE3
@@ -51,6 +51,6 @@
 
 /* Define to 1 if your processor stores words with the most significant byte
    first (like Motorola and SPARC, unlike Intel and VAX). */
-#cmakedefine SNAPPY_IS_BIG_ENDIAN 1
+#cmakedefine01 SNAPPY_IS_BIG_ENDIAN
 
 #endif  // THIRD_PARTY_SNAPPY_OPENSOURCE_CMAKE_CONFIG_H_
diff --git a/snappy-internal.h b/snappy-internal.h
index f1aafa9..8530071 100644
--- a/snappy-internal.h
+++ b/snappy-internal.h
@@ -153,8 +153,9 @@ char* CompressFragment(const char* input,
 // loading from s2 + n.
 //
 // Separate implementation for 64-bit, little-endian cpus.
-#if !defined(SNAPPY_IS_BIG_ENDIAN) && \
-    (defined(__x86_64__) || defined(_M_X64) || defined(ARCH_PPC) || defined(ARCH_ARM))
+#if !SNAPPY_IS_BIG_ENDIAN && \
+    (defined(__x86_64__) || defined(_M_X64) || defined(ARCH_PPC) || \
+     defined(ARCH_ARM))
 static inline std::pair<size_t, bool> FindMatchLength(const char* s1,
                                                       const char* s2,
                                                       const char* s2_limit,
diff --git a/snappy-stubs-internal.h b/snappy-stubs-internal.h
index c2a838f..7d43c92 100644
--- a/snappy-stubs-internal.h
+++ b/snappy-stubs-internal.h
@@ -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 {
diff --git a/snappy-test.cc b/snappy-test.cc
index 7eb490a..aae6072 100644
--- a/snappy-test.cc
+++ b/snappy-test.cc
@@ -151,7 +151,7 @@ LogMessageCrash::~LogMessageCrash() {
 #pragma warning(pop)
 #endif
 
-#ifdef HAVE_LIBZ
+#if HAVE_LIBZ
 
 ZLib::ZLib()
     : comp_init_(false),
diff --git a/snappy-test.h b/snappy-test.h
index f80d343..65f3725 100644
--- a/snappy-test.h
+++ b/snappy-test.h
@@ -31,25 +31,25 @@
 #ifndef THIRD_PARTY_SNAPPY_OPENSOURCE_SNAPPY_TEST_H_
 #define THIRD_PARTY_SNAPPY_OPENSOURCE_SNAPPY_TEST_H_
 
-#ifdef HAVE_CONFIG_H
+#if HAVE_CONFIG_H
 #include "config.h"
 #endif
 
 #include "snappy-stubs-internal.h"
 
-#ifdef HAVE_SYS_MMAN_H
+#if HAVE_SYS_MMAN_H
 #include <sys/mman.h>
 #endif
 
-#ifdef HAVE_SYS_RESOURCE_H
+#if HAVE_SYS_RESOURCE_H
 #include <sys/resource.h>
 #endif
 
-#ifdef HAVE_SYS_TIME_H
+#if HAVE_SYS_TIME_H
 #include <sys/time.h>
 #endif
 
-#ifdef HAVE_WINDOWS_H
+#if HAVE_WINDOWS_H
 // Needed to be able to use std::max without workarounds in the source code.
 // https://support.microsoft.com/en-us/help/143208/prb-using-stl-in-windows-program-can-cause-min-max-conflicts
 #define NOMINMAX
@@ -58,15 +58,15 @@
 
 #define InitGoogle(argv0, argc, argv, remove_flags) ((void)(0))
 
-#ifdef HAVE_LIBZ
+#if HAVE_LIBZ
 #include "zlib.h"
 #endif
 
-#ifdef HAVE_LIBLZO2
+#if HAVE_LIBLZO2
 #include "lzo/lzo1x.h"
 #endif
 
-#ifdef HAVE_LIBLZ4
+#if HAVE_LIBLZ4
 #include "lz4.h"
 #endif
 
@@ -216,7 +216,7 @@ class LogMessageVoidify {
 #define CHECK_GT(a, b) CRASH_UNLESS((a) > (b))
 #define CHECK_OK(cond) (cond).ok()
 
-#ifdef HAVE_LIBZ
+#if HAVE_LIBZ
 
 // Object-oriented wrapper around zlib.
 class ZLib {
diff --git a/snappy_test_tool.cc b/snappy_test_tool.cc
index 24ac1ee..a7c779b 100644
--- a/snappy_test_tool.cc
+++ b/snappy_test_tool.cc
@@ -66,7 +66,7 @@ namespace snappy {
 
 namespace {
 
-#if defined(HAVE_FUNC_MMAP) && defined(HAVE_FUNC_SYSCONF)
+#if HAVE_FUNC_MMAP && HAVE_FUNC_SYSCONF
 
 // To test against code that reads beyond its input, this class copies a
 // string to a newly allocated group of pages, the last of which
@@ -112,7 +112,7 @@ class DataEndingAtUnreadablePage {
   size_t size_;
 };
 
-#else  // defined(HAVE_FUNC_MMAP) && defined(HAVE_FUNC_SYSCONF)
+#else  // HAVE_FUNC_MMAP && HAVE_FUNC_SYSCONF
 
 // Fallback for systems without mmap.
 using DataEndingAtUnreadablePage = std::string;
diff --git a/snappy_unittest.cc b/snappy_unittest.cc
index 8782b52..292004c 100644
--- a/snappy_unittest.cc
+++ b/snappy_unittest.cc
@@ -50,7 +50,7 @@ namespace snappy {
 
 namespace {
 
-#if defined(HAVE_FUNC_MMAP) && defined(HAVE_FUNC_SYSCONF)
+#if HAVE_FUNC_MMAP && HAVE_FUNC_SYSCONF
 
 // To test against code that reads beyond its input, this class copies a
 // string to a newly allocated group of pages, the last of which
@@ -96,7 +96,7 @@ class DataEndingAtUnreadablePage {
   size_t size_;
 };
 
-#else  // defined(HAVE_FUNC_MMAP) && defined(HAVE_FUNC_SYSCONF)
+#else  // HAVE_FUNC_MMAP) && HAVE_FUNC_SYSCONF
 
 // Fallback for systems without mmap.
 using DataEndingAtUnreadablePage = std::string;