[gdb/testsuite] Use -std=c99 in gdb.base/callfuncs.exp

In test-case gdb.base/callfuncs.exp I run into:
...
gdb compile failed, gdb.base/callfuncs.c: In function 't_func_values':
gdb.base/callfuncs.c:611:12: error: too many arguments to function \
  'func_arg1'; expected 0, have 2
  611 |   return ((*func_arg1) (5,5)  == (*func_val1) (5,5)
      |           ~^~~~~~~~~~~  ~
...

Fix this by using -std=c99.

Tested on x86_64-linux.

Approved-By: Tom Tromey <tom@tromey.com>
PR testsuite/32756
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=32756

diff --git a/gdb/testsuite/gdb.base/callfuncs.exp b/gdb/testsuite/gdb.base/callfuncs.exp
index d4a53e803c625f6a7213fa8e508d8a07c3c17a53..d7640aba4f3bca2d9bc5d10389bd9e41bda15a83 100644 (file)
--- a/gdb/testsuite/gdb.base/callfuncs.exp
+++ b/gdb/testsuite/gdb.base/callfuncs.exp
@@ -18,9 +18,19 @@
 
 standard_testfile
 
+set compile_flags {}
+lappend compile_flags debug
+
 # We still want to test non-prototype functions for now, which is why
 # we disable compilers warning about them.
-set compile_flags {debug additional_flags=-Wno-deprecated-non-prototype}
+lappend compile_flags additional_flags=-Wno-deprecated-non-prototype
+
+if {[have_compile_flag -std=c99]} {
+    # Gcc 15 defaults to c23, which no longer supports unprototyped functions.
+    # Use a c dialect that does support this.
+    lappend compile_flags additional_flags=-std=c99
+}
+
 if {[support_complex_tests]} {
     lappend compile_flags "additional_flags=-DTEST_COMPLEX"
 }