c-family: Prevent -Wformat warnings with u8 strings [PR105626]
The <https://gcc.gnu.org/pipermail/gcc/2022-May/238679.html> thread
seems to have concluded that -Wformat shouldn't warn about
printf((const char*) u8"test %d\n", 1);
saying "format string is not an array of type 'char'". This code
is not an aliasing violation, and there are no I/O functions for u8
strings, so the const char * cast is OK and shouldn't be disregarded.
PR c++/105626
gcc/c-family/ChangeLog:
* c-format.cc (check_format_arg): Don't emit -Wformat warnings with
u8 strings.
gcc/testsuite/ChangeLog:
* g++.dg/warn/Wformat-char8_t-1.C: New test.
diff --git a/gcc/c-family/c-format.cc b/gcc/c-family/c-format.cc
index 4559ca3..7547804 100644
--- a/gcc/c-family/c-format.cc
+++ b/gcc/c-family/c-format.cc
@@ -1742,7 +1742,8 @@
}
tree underlying_type
= TYPE_MAIN_VARIANT (TREE_TYPE (TREE_TYPE (format_tree)));
- if (underlying_type != char_type_node)
+ if (underlying_type != char_type_node
+ && !(flag_char8_t && underlying_type == char8_type_node))
{
if (underlying_type == char16_type_node
|| underlying_type == char32_type_node
diff --git a/gcc/testsuite/g++.dg/warn/Wformat-char8_t-1.C b/gcc/testsuite/g++.dg/warn/Wformat-char8_t-1.C
new file mode 100644
index 0000000..ba6f388
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wformat-char8_t-1.C
@@ -0,0 +1,10 @@
+// PR c++/105626
+// { dg-do compile { target c++11 } }
+// { dg-options "-Wformat" }
+// { dg-additional-options "-fchar8_t" { target c++17_down } }
+
+int main()
+{
+ __builtin_printf((const char*) u8"test %d\n", 1); // { dg-bogus "format string" }
+ return 0;
+}
