Re: error: Support the compiler's control flow analysis better

[Bruno Haible]

Pádraig Brady wrote:
> >> We might need to cast STATUS to bool to avoid the
> >> following failure from coreutils CI:

What you call a failure is in fact a warning. Adding -Werror is your
responsibility.

> >> In file included from src/die.h:22,
> >>                     from src/chroot.c:27:
> >> src/chroot.c: In function 'main':
> >> src/chroot.c:362:25: error: '?:'using integer constants in boolean context 
> >> [-Werror=int-in-bool-context]
> >>      362 |         error (warn ? 0 : EXIT_CANCELED, 0, "%s", (err));
> >> ./lib/error.h:422:33: note: in definition of macro 'error'
> >>      422 |      ((error)(0, __VA_ARGS__), (status) ? exit (status) : 
> >> (void)0)
> >>          |                                 ^~~~~~
> > 
> > Actually casting with (bool), or using !! does NOT help here.
> To avoid this one can use `(status) != 0`.

What this code is meant to do is to test status against 0. Writing it
like this is the obvious fix. Done as shown below.

> There still is a gotcha (hit in dd.c in coreutils)
> where if you define an error macro yourself
> you get a macro redefinition error,

You can #define _GL_NO_INLINE_ERROR if you don't like gnulib's override.


2023-05-28  Bruno Haible  <bruno@clisp.org>

        error: Avoid -Wint-in-bool-context warning.
        Reported by Pádraig Brady in
        <https://lists.gnu.org/archive/html/bug-gnulib/2023-05/msg00178.html>.
        * lib/error.in.h (error, error_at_line): Use 'status != 0', since status
        is expected to be an int, not a bool value.

diff --git a/lib/error.in.h b/lib/error.in.h
index 4bf191e102..70fb132133 100644
--- a/lib/error.in.h
+++ b/lib/error.in.h
@@ -69,7 +69,7 @@ _GL_CXXALIAS_RPL (error, void,
 # ifndef _GL_NO_INLINE_ERROR
 #  undef error
 #  define error(status, ...) \
-     ((rpl_error)(0, __VA_ARGS__), (status) ? exit (status) : (void)0)
+     ((rpl_error)(0, __VA_ARGS__), (status) != 0 ? exit (status) : (void)0)
 # endif
 #else
 # if ! @HAVE_ERROR@
@@ -81,7 +81,7 @@ _GL_CXXALIAS_SYS (error, void,
                   (int __status, int __errnum, const char *__format, ...));
 # ifndef _GL_NO_INLINE_ERROR
 #  define error(status, ...) \
-     ((error)(0, __VA_ARGS__), (status) ? exit (status) : (void)0)
+     ((error)(0, __VA_ARGS__), (status) != 0 ? exit (status) : (void)0)
 # endif
 #endif
 #if __GLIBC__ >= 2
@@ -105,7 +105,7 @@ _GL_CXXALIAS_RPL (error_at_line, void,
 # ifndef _GL_NO_INLINE_ERROR
 #  undef error_at_line
 #  define error_at_line(status, ...) \
-     ((rpl_error_at_line)(0, __VA_ARGS__), (status) ? exit (status) : (void)0)
+     ((rpl_error_at_line)(0, __VA_ARGS__), (status) != 0 ? exit (status) : 
(void)0)
 # endif
 #else
 # if ! @HAVE_ERROR_AT_LINE@
@@ -119,7 +119,7 @@ _GL_CXXALIAS_SYS (error_at_line, void,
                    unsigned int __lineno, const char *__format, ...));
 # ifndef _GL_NO_INLINE_ERROR
 #  define error_at_line(status, ...) \
-     ((error_at_line)(0, __VA_ARGS__), (status) ? exit (status) : (void)0)
+     ((error_at_line)(0, __VA_ARGS__), (status) != 0 ? exit (status) : (void)0)
 # endif
 #endif
 _GL_CXXALIASWARN (error_at_line);