fix 'ignoring return value' compiler warnings

Various system functions like write() are marked with the
__warn_unused_result__ attribute, which causes an 'ignoring return value'
warning to be emitted, even if the function call result is cast to (void).

The generic solution seems to be

    int rc = write(...);
    PERL_UNUSED_VAR(rc);

1 files changed, 5 insertions, 2 deletions

diff --git a/perlio.c b/perlio.c
index 60b6a596f0..d89b9bb576 100644
--- a/perlio.c
+++ b/perlio.c
@@ -457,13 +457,14 @@ PerlIO_debug(const char *fmt, ...)
 	}
     }
     if (PL_perlio_debug_fd > 0) {
+        int rc = 0;
 #ifdef USE_ITHREADS
 	const char * const s = CopFILE(PL_curcop);
 	/* Use fixed buffer as sv_catpvf etc. needs SVs */
 	char buffer[1024];
 	const STRLEN len1 = my_snprintf(buffer, sizeof(buffer), "%.40s:%" IVdf " ", s ? s : "(none)", (IV) CopLINE(PL_curcop));
 	const STRLEN len2 = my_vsnprintf(buffer + len1, sizeof(buffer) - len1, fmt, ap);
-	(void)PerlLIO_write(PL_perlio_debug_fd, buffer, len1 + len2);
+	rc = PerlLIO_write(PL_perlio_debug_fd, buffer, len1 + len2);
 #else
 	const char *s = CopFILE(PL_curcop);
 	STRLEN len;
@@ -472,9 +473,11 @@ PerlIO_debug(const char *fmt, ...)
 	Perl_sv_vcatpvf(aTHX_ sv, fmt, &ap);
 
 	s = SvPV_const(sv, len);
-	(void)PerlLIO_write(PL_perlio_debug_fd, s, len);
+	rc = PerlLIO_write(PL_perlio_debug_fd, s, len);
 	SvREFCNT_dec(sv);
 #endif
+        /* silently ignore failures */
+        PERL_UNUSED_VAR(rc);
     }
     va_end(ap);
 }