From 65941a910911a8d452b6a6baaccafcc7a1d85c1f Mon Sep 17 00:00:00 2001 From: Marek Polacek Date: Tue, 5 Jul 2022 14:22:26 -0400 Subject: [PATCH] c-family: Prevent -Wformat warnings with u8 strings [PR105626] The 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. (cherry picked from commit 543828e79bfa63ef26b11a2c9ea81fd7905f33aa) --- gcc/c-family/c-format.cc | 3 ++- gcc/testsuite/g++.dg/warn/Wformat-char8_t-1.C | 10 ++++++++++ 2 files changed, 12 insertions(+), 1 deletion(-) create mode 100644 gcc/testsuite/g++.dg/warn/Wformat-char8_t-1.C diff --git a/gcc/c-family/c-format.cc b/gcc/c-family/c-format.cc index 98f28c0..ebdac57 100644 --- a/gcc/c-family/c-format.cc +++ b/gcc/c-family/c-format.cc @@ -1748,7 +1748,8 @@ check_format_arg (void *ctx, tree format_tree, } 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; +} -- 2.7.4