[gcc r13-5335] c++: "" #pragma at BOF [PR108504]

[Jason Merrill <jason@gcc.gnu.org>]

https://gcc.gnu.org/g:327d45c57ebd2655a7599df0f01b8b5e2f82eda7

commit r13-5335-g327d45c57ebd2655a7599df0f01b8b5e2f82eda7
Author: Jason Merrill <jason@redhat.com>
Date:   Tue Jan 24 16:26:50 2023 -0500

    c++: "" #pragma at BOF [PR108504]
    
    Since r11-2095 we pass flags to cp_lexer_get_preprocessor_token, and
    cp_lexer_new_main passes C_LEX_STRING_NO_JOIN when lexing most of the
    translation unit, but doesn't do that for the very first token; as a
    result, if the first token is a string literal, we try to join strings and
    get confused if that encounters a pragma.
    
            PR c++/108504
    
    gcc/cp/ChangeLog:
    
            * parser.cc (cp_lexer_new_main): Pass C_LEX_STRING_NO_JOIN for first
            token, too.
    
    gcc/testsuite/ChangeLog:
    
            * g++.dg/ext/pragma1.C: New test.

Diff:
---
 gcc/cp/parser.cc                   | 2 +-
 gcc/testsuite/g++.dg/ext/pragma1.C | 4 ++++
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc
index b38c22e9a3d..07ec0e14491 100644
--- a/gcc/cp/parser.cc
+++ b/gcc/cp/parser.cc
@@ -705,7 +705,7 @@ cp_lexer_new_main (void)
   /* It's possible that parsing the first pragma will load a PCH file,
      which is a GC collection point.  So we have to do that before
      allocating any memory.  */
-  cp_lexer_get_preprocessor_token (0, &token);
+  cp_lexer_get_preprocessor_token (C_LEX_STRING_NO_JOIN, &token);
   cp_parser_initial_pragma (&token);
   c_common_no_more_pch ();
 
diff --git a/gcc/testsuite/g++.dg/ext/pragma1.C b/gcc/testsuite/g++.dg/ext/pragma1.C
new file mode 100644
index 00000000000..bb258dac9a7
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/pragma1.C
@@ -0,0 +1,4 @@
+// PR c++/108504
+
+"1"				// { dg-error "" }
+#pragma GCC diagnostic push