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From: "matthewp515 at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug preprocessor/97498] New: #pragma GCC diagnostic ignored
 "-Wunused-function" inconsistent
Date: Mon, 19 Oct 2020 23:49:57 +0000
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X-Bugzilla-Version: 9.3.0
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D97498

            Bug ID: 97498
           Summary: #pragma GCC diagnostic ignored "-Wunused-function"
                    inconsistent
           Product: gcc
           Version: 9.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: preprocessor
          Assignee: unassigned at gcc dot gnu.org
          Reporter: matthewp515 at gmail dot com
  Target Milestone: ---

Ubuntu Linux 20.04


#define STR(x) #x
#define WIGNORE(x, instrs) \
        _Pragma("GCC diagnostic push") \
        _Pragma(STR(GCC diagnostic ignored #x)) \
        instrs \
        _Pragma("GCC diagnostic pop")

// REPLACE

int main(void) {return 1;}


When REPLACE is replaced with:

WIGNORE(-Wunused-function,
static int f(int a) {return a + 1;}
)

The command:

gcc main.c -Wall -Werror -Wextra

fails (-Werror=3Dunused-function). However, breaking up the command into se=
parate
preprocessing and compilation stages:

gcc -E main.c -Wall -Werror -Wextra | gcc -x c -

passes.

When the macro is unwound by REPLACE being replaced with:

_Pragma("GCC diagnostic push");
_Pragma("GCC diagnostic ignored \"-Wunused-function\"");
static int f(int p) {return p + 1;}
_Pragma("GCC diagnostic pop");

The first command then passes. By adding a single backslash (\) right after=
 the
implementation of f, as is required to keep the WIGNORE macro all as one, t=
he
command fails. But how else can the macro be constructed?=