C2X adds BOOL_MAX and BOOL_WIDTH macros to <limits.h>. As GCC only
supports values 0 and 1 for _Bool (regardless of the number of bits in
the representation, other bits are padding bits and if any of them are
nonzero, the representation is a trap representation), the values of
those macros can just be hardcoded directly in <limits.h> rather than
needing corresponding predefined macros.
Bootstrapped with no regressions on x86_64-pc-linux-gnu. OK to
commit?
gcc/
2020-07-02 Joseph Myers <jos...@codesourcery.com>
* glimits.h [__STDC_VERSION__ > 201710L] (BOOL_MAX, BOOL_WIDTH):
New macros.
gcc/testsuite/
2020-07-02 Joseph Myers <jos...@codesourcery.com>
* gcc.dg/c11-bool-limits-1.c, gcc.dg/c2x-bool-limits-1.c: New
tests.
diff --git a/gcc/glimits.h b/gcc/glimits.h
index a37f496ef1b..50927510677 100644
--- a/gcc/glimits.h
+++ b/gcc/glimits.h
@@ -150,4 +150,12 @@ see the files COPYING3 and COPYING.RUNTIME respectively.
If not, see
# define ULLONG_WIDTH __LONG_LONG_WIDTH__
#endif
+#if defined (__STDC_VERSION__) && __STDC_VERSION__ > 201710L
+/* C2X width and limit of _Bool. */
+# undef BOOL_MAX
+# define BOOL_MAX 1
+# undef BOOL_WIDTH
+# define BOOL_WIDTH 1
+#endif
+
#endif /* _LIMITS_H___ */
diff --git a/gcc/testsuite/gcc.dg/c11-bool-limits-1.c
b/gcc/testsuite/gcc.dg/c11-bool-limits-1.c
new file mode 100644
index 00000000000..9ca29be4d72
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/c11-bool-limits-1.c
@@ -0,0 +1,13 @@
+/* Test limits for _Bool not in <limits.h> in C11. */
+/* { dg-do compile } */
+/* { dg-options "-std=c11" } */
+
+#include <limits.h>
+
+#ifdef BOOL_MAX
+# error "unexpected BOOL_MAX"
+#endif
+
+#ifdef BOOL_WIDTH
+# error "unexpected BOOL_WIDTH"
+#endif
diff --git a/gcc/testsuite/gcc.dg/c2x-bool-limits-1.c
b/gcc/testsuite/gcc.dg/c2x-bool-limits-1.c
new file mode 100644
index 00000000000..d32b4ef59ed
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/c2x-bool-limits-1.c
@@ -0,0 +1,19 @@
+/* Test limits for _Bool in <limits.h> in C2x. */
+/* { dg-do compile } */
+/* { dg-options "-std=c2x" } */
+
+#include <limits.h>
+
+#ifndef BOOL_MAX
+# error "missing BOOL_MAX"
+#endif
+
+#ifndef BOOL_WIDTH
+# error "missing BOOL_WIDTH"
+#endif
+
+/* In principle _Bool can support values wider than 1 bit, stored via
+ type punning, but this is not supported by GCC. */
+
+_Static_assert (BOOL_MAX == 1, "bad BOOL_MAX");
+_Static_assert (BOOL_WIDTH == 1, "bad BOOL_WIDTH");
--
Joseph S. Myers
jos...@codesourcery.com
