[gcc r13-2689] float.h: Do not define INFINITY for C2x when infinities not supported

[Joseph Myers <jsm28@gcc.gnu.org>]

https://gcc.gnu.org/g:6248f4ff67502c88d92f55fa5ea5996937220e5c

commit r13-2689-g6248f4ff67502c88d92f55fa5ea5996937220e5c
Author: Joseph Myers <joseph@codesourcery.com>
Date:   Thu Sep 15 20:10:42 2022 +0000

    float.h: Do not define INFINITY for C2x when infinities not supported
    
    C2x has changed the rules for defining INFINITY in <float.h> so it is
    no longer defined when float does not support infinities, instead of
    being defined to an expression that overflows at translation time.
    Thus, make the definition conditional on __FLT_HAS_INFINITY__ (this is
    already inside a C2x-conditional part of <float.h>, because previous C
    standard versions only had this macro in <math.h>).
    
    Bootstrapped with no regressions for x86_64-pc-linux-gnu.  Also did a
    spot test of the case of no infinities supported by building cc1 for
    vax-netbsdelf and testing compiling the new c2x-float-11.c test with
    it.
    
    gcc/
            * ginclude/float.h (INFINITY): Define only if
            [__FLT_HAS_INFINITY__].
    
    gcc/testsuite/
            * gcc.dg/c2x-float-2.c: Require inff effective-target.
            * gcc.dg/c2x-float-11.c: New test.

Diff:
---
 gcc/ginclude/float.h                | 4 +++-
 gcc/testsuite/gcc.dg/c2x-float-11.c | 9 +++++++++
 gcc/testsuite/gcc.dg/c2x-float-2.c  | 4 ++--
 3 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/gcc/ginclude/float.h b/gcc/ginclude/float.h
index 9d368c4afa5..afe4a712878 100644
--- a/gcc/ginclude/float.h
+++ b/gcc/ginclude/float.h
@@ -257,9 +257,11 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 #define DBL_IS_IEC_60559	__DBL_IS_IEC_60559__
 #define LDBL_IS_IEC_60559	__LDBL_IS_IEC_60559__
 
-/* Infinity in type float, or overflow if infinity not supported.  */
+/* Infinity in type float; not defined if infinity not supported.  */
+#if __FLT_HAS_INFINITY__
 #undef INFINITY
 #define INFINITY	(__builtin_inff ())
+#endif
 
 /* Quiet NaN, if supported for float.  */
 #if __FLT_HAS_QUIET_NAN__
diff --git a/gcc/testsuite/gcc.dg/c2x-float-11.c b/gcc/testsuite/gcc.dg/c2x-float-11.c
new file mode 100644
index 00000000000..0e2f3c0c97a
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/c2x-float-11.c
@@ -0,0 +1,9 @@
+/* Test INFINITY macro.  Test when infinities not supported.  */
+/* { dg-do compile { target { ! inff } } } */
+/* { dg-options "-std=c2x" } */
+
+#include <float.h>
+
+#ifdef INFINITY
+#error "INFINITY defined"
+#endif
diff --git a/gcc/testsuite/gcc.dg/c2x-float-2.c b/gcc/testsuite/gcc.dg/c2x-float-2.c
index 4f669fd39bc..61a77f6f2db 100644
--- a/gcc/testsuite/gcc.dg/c2x-float-2.c
+++ b/gcc/testsuite/gcc.dg/c2x-float-2.c
@@ -1,8 +1,8 @@
-/* Test INFINITY macro.  Generic test even if infinities not
-   supported.  */
+/* Test INFINITY macro.  Generic test.  */
 /* { dg-do run } */
 /* { dg-options "-std=c2x -w" } */
 /* { dg-add-options ieee } */
+/* { dg-require-effective-target inff } */
 
 #include <float.h>