[PATCH 1/2] Port better to GCC under macOS

[Paul Eggert]

Work around macOS header that has ‘#define __has_builtin(x) 0’
when compiled by GCC.  Apple really, really doesn’t want you to
use GCC, apparently.  Rroblem reported by Akim Demaille in:
https://lists.gnu.org/r/bug-bison/2019-10/msg00071.html
The fix is to not trust __has_builtin when being compiled by
recent-enough GCC.
* lib/intprops.h (__has_builtin)
(_GL_HAS___builtin_add_overflow, _GL_TEMPDEF___has_builtin):
* lib/verify.h (__has_builtin, _GL_HAS___builtin_unreachable)
(_GL_HAS___builtin_trap, _GL_TEMPDEF___has_builtin):
Remove.  All uses removed.
* lib/intprops.h (_GL_HAS_BUILTIN_ADD_OVERFLOW): Use __has_builtin
directly, if defined and if not newer GCC.
* lib/verify.h (_GL_HAS_BUILTIN_TRAP, _GL_HAS_BUILTIN_UNREACHABLE):
New macro, that use __has_builtin directly, if defined and if
not newer GCC.
(assume): Use them.
---
 ChangeLog      | 21 +++++++++++++++++++++
 lib/intprops.h | 22 +++-------------------
 lib/verify.h   | 37 ++++++++++++++++++-------------------
 3 files changed, 42 insertions(+), 38 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index fc438f503..103befc64 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,24 @@
+2019-10-23  Paul Eggert  <address@hidden>
+
+       Port better to GCC under macOS
+       Work around macOS header that has ‘#define __has_builtin(x) 0’
+       when compiled by GCC.  Apple really, really doesn’t want you to
+       use GCC, apparently.  Rroblem reported by Akim Demaille in:
+       https://lists.gnu.org/r/bug-bison/2019-10/msg00071.html
+       The fix is to not trust __has_builtin when being compiled by
+       recent-enough GCC.
+       * lib/intprops.h (__has_builtin)
+       (_GL_HAS___builtin_add_overflow, _GL_TEMPDEF___has_builtin):
+       * lib/verify.h (__has_builtin, _GL_HAS___builtin_unreachable)
+       (_GL_HAS___builtin_trap, _GL_TEMPDEF___has_builtin):
+       Remove.  All uses removed.
+       * lib/intprops.h (_GL_HAS_BUILTIN_ADD_OVERFLOW): Use __has_builtin
+       directly, if defined and if not newer GCC.
+       * lib/verify.h (_GL_HAS_BUILTIN_TRAP, _GL_HAS_BUILTIN_UNREACHABLE):
+       New macro, that use __has_builtin directly, if defined and if
+       not newer GCC.
+       (assume): Use them.
+
 2019-10-22  Akim Demaille  <address@hidden>
 
        maintainer-makefile: update rule for argmatch.
diff --git a/lib/intprops.h b/lib/intprops.h
index ffd737028..bc7e950a0 100644
--- a/lib/intprops.h
+++ b/lib/intprops.h
@@ -22,18 +22,6 @@
 
 #include <limits.h>
 
-/* If the compiler lacks __has_builtin, define it well enough for this
-   source file only.  */
-#ifndef __has_builtin
-# define __has_builtin(x) _GL_HAS_##x
-# if 5 <= __GNUC__ && !defined __ICC
-#  define _GL_HAS___builtin_add_overflow 1
-# else
-#  define _GL_HAS___builtin_add_overflow 0
-# endif
-# define _GL_TEMPDEF___has_builtin
-#endif
-
 /* Return a value with the common real type of E and V and the value of V.
    Do not evaluate E.  */
 #define _GL_INT_CONVERT(e, v) ((1 ? 0 : (e)) + (v))
@@ -234,8 +222,10 @@
 
 /* True if __builtin_add_overflow (A, B, P) and __builtin_sub_overflow
    (A, B, P) work when P is non-null.  */
-#if __has_builtin (__builtin_add_overflow)
+#if 5 <= __GNUC__ && !defined __ICC
 # define _GL_HAS_BUILTIN_ADD_OVERFLOW 1
+#elif defined __has_builtin
+# define _GL_HAS_BUILTIN_ADD_OVERFLOW __has_builtin (__builtin_add_overflow)
 #else
 # define _GL_HAS_BUILTIN_ADD_OVERFLOW 0
 #endif
@@ -586,10 +576,4 @@
          : (tmin) / (a) < (b)) \
       : (tmax) / (b) < (a)))
 
-#ifdef _GL_TEMPDEF___has_builtin
-# undef __has_builtin
-# undef _GL_HAS___builtin_add_overflow
-# undef _GL_TEMPDEF___has_builtin
-#endif
-
 #endif /* _GL_INTPROPS_H */
diff --git a/lib/verify.h b/lib/verify.h
index 06e975ebf..a58005c39 100644
--- a/lib/verify.h
+++ b/lib/verify.h
@@ -56,16 +56,6 @@
 # undef _Static_assert
 #endif
 
-/* If the compiler lacks __has_builtin, define it well enough for this
-   source file only.  */
-#ifndef __has_builtin
-# define __has_builtin(x) _GL_HAS_##x
-# define _GL_HAS___builtin_unreachable (4 < __GNUC__ + (5 <= __GNUC_MINOR__))
-# define _GL_HAS___builtin_trap \
-    (3 < __GNUC__ + (3 < __GNUC_MINOR__ + (4 <= __GNUC_PATCHLEVEL__)))
-# define _GL_TEMPDEF___has_builtin
-#endif
-
 /* Each of these macros verifies that its argument R is nonzero.  To
    be portable, R should be an integer constant expression.  Unlike
    assert (R), there is no run-time overhead.
@@ -243,6 +233,22 @@ template <int w>
 
 /* @assert.h omit start@  */
 
+#if 3 < __GNUC__ + (3 < __GNUC_MINOR__ + (4 <= __GNUC_PATCHLEVEL__))
+# define _GL_HAS_BUILTIN_TRAP 1
+#elif defined __has_builtin
+# define _GL_HAS_BUILTIN_TRAP __has_builtin (__builtin_trap)
+#else
+# define _GL_HAS_BUILTIN_TRAP 0
+#endif
+
+#if 4 < __GNUC__ + (5 <= __GNUC_MINOR__)
+# define _GL_HAS_BUILTIN_UNREACHABLE 1
+#elif defined __has_builtin
+# define _GL_HAS_BUILTIN_UNREACHABLE __has_builtin (__builtin_unreachable)
+#else
+# define _GL_HAS_BUILTIN_UNREACHABLE 0
+#endif
+
 /* Each of these macros verifies that its argument R is nonzero.  To
    be portable, R should be an integer constant expression.  Unlike
    assert (R), there is no run-time overhead.
@@ -276,11 +282,11 @@ template <int w>
    can suffer if R uses hard-to-optimize features such as function
    calls not inlined by the compiler.  */
 
-#if __has_builtin (__builtin_unreachable)
+#if _GL_HAS_BUILTIN_UNREACHABLE
 # define assume(R) ((R) ? (void) 0 : __builtin_unreachable ())
 #elif 1200 <= _MSC_VER
 # define assume(R) __assume (R)
-#elif (defined GCC_LINT || defined lint) && __has_builtin (__builtin_trap)
+#elif (defined GCC_LINT || defined lint) && _GL_HAS_BUILTIN_TRAP
   /* Doing it this way helps various packages when configured with
      --enable-gcc-warnings, which compiles with -Dlint.  It's nicer
      when 'assume' silences warnings even with older GCCs.  */
@@ -290,13 +296,6 @@ template <int w>
 # define assume(R) ((R) ? (void) 0 : /*NOTREACHED*/ (void) 0)
 #endif
 
-#ifdef _GL_TEMPDEF___has_builtin
-# undef __has_builtin
-# undef _GL_HAS___builtin_unreachable
-# undef _GL_HAS___builtin_trap
-# undef _GL_TEMPDEF___has_builtin
-#endif
-
 /* @assert.h omit end@  */
 
 #endif
-- 
2.21.0