[Bug c/117977] New: duplicated warnings output

[alexey.lapshin at espressif dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117977

            Bug ID: 117977
           Summary: duplicated warnings output
           Product: gcc
           Version: 15.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: alexey.lapshin at espressif dot com
  Target Milestone: ---

Test code:

#include <stddef.h>
#include <assert.h>

#define SPI1_HOST 1
#define SPI_HOST  _Pragma ("GCC warning \"use SPI1_HOST\"")  SPI1_HOST
#define ERROR_CHECK(x) do { \
        assert(x);          \
    } while(0)

int foo(int host_id, void *ptr) {
    ptr = ptr;
    return host_id;
}

void main(void) {
    ERROR_CHECK(foo(SPI_HOST,
                    NULL));
}


Compiling with the latest GCC (15.0) gives doubled warnings:
In file included from <source>:2:
<source>:5:21: warning: use SPI1_HOST
    5 | #define SPI_HOST    _Pragma ("GCC warning \"use SPI1_HOST\"") 
SPI1_HOST
      |                     ^~~~~~~
<source>:16:5: note: in expansion of macro 'ERROR_CHECK'
   16 |     ERROR_CHECK(foo(SPI_HOST,
      |     ^~~~~~~~~~~
<source>:16:21: note: in expansion of macro 'SPI_HOST'
   16 |     ERROR_CHECK(foo(SPI_HOST,
      |                     ^~~~~~~~
<source>:5:21: warning: use SPI1_HOST
    5 | #define SPI_HOST    _Pragma ("GCC warning \"use SPI1_HOST\"") 
SPI1_HOST
      |                     ^~~~~~~
<source>:16:5: note: in expansion of macro 'ERROR_CHECK'
   16 |     ERROR_CHECK(foo(SPI_HOST,
      |     ^~~~~~~~~~~
<source>:16:21: note: in expansion of macro 'SPI_HOST'
   16 |     ERROR_CHECK(foo(SPI_HOST,
      |                     ^~~~~~~~



This is a bit weird because the preprocessor outputs only one use of _Pragma.

C++ front-end handles this as expected.


https://godbolt.org/z/ov3K3h5aP