https://gcc.gnu.org/g:c3bc2787b8beb7aae67fdf2a7f7271a9a4edca7c
commit r15-91-gc3bc2787b8beb7aae67fdf2a7f7271a9a4edca7c
Author: Jason Merrill <ja...@redhat.com>
Date: Mon Feb 12 18:24:00 2024 -0500
c++: const void* memchr [PR113706]
The C++ standard specifies that the <string.h> functions have const and
non-const overloads, unlike C's single function with const argument and
non-const return. Many systems don't actually implement this, but only add
an overload with non-const argument, so both end up having non-const return.
Solaris <string.h> does what the standard says, but we were penalizing it by
not recognizing the const overload as the built-in memchr.
PR c++/113706
gcc/cp/ChangeLog:
* decl.cc (decls_match): Handle memchr return type being
const-qualified.
gcc/testsuite/ChangeLog:
* g++.dg/opt/const-builtin1.C: New test.
* c-c++-common/pr103798-2.c: Remove xfail.
Diff:
---
gcc/cp/decl.cc | 10 ++++++++++
gcc/testsuite/c-c++-common/pr103798-2.c | 3 +--
gcc/testsuite/g++.dg/opt/const-builtin1.C | 33 +++++++++++++++++++++++++++++++
3 files changed, 44 insertions(+), 2 deletions(-)
diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
index d88e0698652..df855334133 100644
--- a/gcc/cp/decl.cc
+++ b/gcc/cp/decl.cc
@@ -1156,6 +1156,16 @@ decls_match (tree newdecl, tree olddecl, bool
record_versions /* = true */)
tree r2 = fndecl_declared_return_type (olddecl);
tree r1 = fndecl_declared_return_type (newdecl);
+ /* For memchr et al, allow const void* return type (as specified by C++)
+ when we expect void* (as in C). */
+ if (DECL_IS_UNDECLARED_BUILTIN (olddecl)
+ && DECL_EXTERN_C_P (olddecl)
+ && !same_type_p (r1, r2)
+ && TREE_CODE (r1) == POINTER_TYPE
+ && TREE_CODE (r2) == POINTER_TYPE
+ && comp_ptr_ttypes (TREE_TYPE (r1), TREE_TYPE (r2)))
+ r2 = r1;
+
tree p1 = TYPE_ARG_TYPES (f1);
tree p2 = TYPE_ARG_TYPES (f2);
diff --git a/gcc/testsuite/c-c++-common/pr103798-2.c
b/gcc/testsuite/c-c++-common/pr103798-2.c
index 83cdfaa1660..e7e99c3679e 100644
--- a/gcc/testsuite/c-c++-common/pr103798-2.c
+++ b/gcc/testsuite/c-c++-common/pr103798-2.c
@@ -27,5 +27,4 @@ main ()
return 0;
}
-/* See PR c++/113706 for the xfail. */
-/* { dg-final { scan-assembler-not "memchr" { xfail { c++ && { *-*-solaris2*
*-*-vxworks* } } } } } */
+/* { dg-final { scan-assembler-not "memchr" } } */
diff --git a/gcc/testsuite/g++.dg/opt/const-builtin1.C
b/gcc/testsuite/g++.dg/opt/const-builtin1.C
new file mode 100644
index 00000000000..8b9987271c0
--- /dev/null
+++ b/gcc/testsuite/g++.dg/opt/const-builtin1.C
@@ -0,0 +1,33 @@
+// PR c++/113706
+/* A variant of the pr103798-2.c test with const void * memchr return type, as
+ specified by the C++ standard. */
+/* { dg-do run } */
+/* { dg-options "-O2 -fdump-tree-optimized -save-temps" } */
+
+extern "C" const void *memchr (const void *, int, __SIZE_TYPE__); // {
dg-bogus "built-in" }
+
+__attribute__ ((weak))
+int
+f (int a)
+{
+ return memchr ("aE", a, 2) != 0;
+}
+
+__attribute__ ((weak))
+int
+g (char a)
+{
+ return a == 'a' || a == 'E';
+}
+
+int
+main ()
+{
+ for (int i = 0; i < 255; i++)
+ if (f (i + 256) != g (i + 256))
+ __builtin_abort ();
+
+ return 0;
+}
+
+/* { dg-final { scan-assembler-not "memchr" } } */
