commit 2084e7ca4d344c39eb39e53848b51b5d84444414 Author: Joseph Myers Date: Wed Dec 10 00:41:19 2014 +0000 Add macros for diagnostic control, use for scanf %a tests. In , Roland requested internal macros for use of "#pragma GCC diagnostic". This patch adds such macros and uses them to disable -Wformat warnings for some code testing GNU scanf %as where GCC expects C99 scanf %a (several other stdio tests currently use -Wno-format to disable warnings). Limitations in GCC's diagnostic pragmas require separate macros before and after the code generating the warnings, rather than a single macro taking that code as an argument. The macros are named DIAG_*_NEEDS_COMMENT to emphasise to reviewers the need for a comment accompanying any use of them (such comments may however just appear once for several uses of the macros for the same issue in the same file). I put a GCC version in the arguments to DIAG_IGNORE_NEEDS_COMMENT, as that seems something useful to grep for when obsoleting support for an old GCC version and needing to decide if warning-disabling code is still relevant. These macros should be usable for replacing existing -Wno-* use in makefiles (as also suggested by Roland), though I have no plans to work on that (only on use of the macros in cases where warnings are currently present that need disabling to use -Werror). Tested for x86_64. * include/libc-internal.h (DIAG_PUSH_NEEDS_COMMENT): New macro. (DIAG_POP_NEEDS_COMMENT): Likewise. (_DIAG_STR1): Likewise. (_DIAG_STR): Likewise. (DIAG_IGNORE_NEEDS_COMMENT): Likewise. * stdio-common/bug21.c: Include . (do_test): Disable -Wformat around call to sscanf. * stdio-common/scanf14.c: Include . (main): Disable -Wformat around some calls to scanf functions. diff --git a/include/libc-internal.h b/include/libc-internal.h index 2ced1c17d3dff93d..bca59a46144b736f 100644 --- a/include/libc-internal.h +++ b/include/libc-internal.h @@ -76,4 +76,35 @@ extern void __init_misc (int, char **, char **); #define ignore_value(x) \ ({ __typeof__ (x) __ignored_value = (x); (void) __ignored_value; }) +/* The macros to control diagnostics are structured like this, rather + than a single macro that both pushes and pops diagnostic state and + takes the affected code as an argument, because the GCC pragmas + work by disabling the diagnostic for a range of source locations + and do not work when all the pragmas and the affected code are in a + single macro expansion. */ + +/* Push diagnostic state. */ +#define DIAG_PUSH_NEEDS_COMMENT _Pragma ("GCC diagnostic push") + +/* Pop diagnostic state. */ +#define DIAG_POP_NEEDS_COMMENT _Pragma ("GCC diagnostic pop") + +#define _DIAG_STR1(s) #s +#define _DIAG_STR(s) _DIAG_STR1(s) + +/* Ignore the diagnostic OPTION. VERSION is the most recent GCC + version for which the diagnostic has been confirmed to appear in + the absence of the pragma (in the form MAJOR.MINOR for GCC 4.x, + just MAJOR for GCC 5 and later). Uses of this pragma should be + reviewed when the GCC version given is no longer supported for + building glibc; the version number should always be on the same + source line as the macro name, so such uses can be found with grep. + Uses should come with a comment giving more details of the + diagnostic, and an architecture on which it is seen if possibly + optimization-related and not in architecture-specific code. This + macro should only be used if the diagnostic seems hard to fix (for + example, optimization-related false positives). */ +#define DIAG_IGNORE_NEEDS_COMMENT(version, option) \ + _Pragma (_DIAG_STR (GCC diagnostic ignored option)) + #endif /* _LIBC_INTERNAL */ diff --git a/stdio-common/bug21.c b/stdio-common/bug21.c index d22b9c1a9717a197..ca27272ba191321e 100644 --- a/stdio-common/bug21.c +++ b/stdio-common/bug21.c @@ -1,4 +1,5 @@ #include +#include static int do_test (void) @@ -6,7 +7,15 @@ do_test (void) static const char buf[] = " "; char *str; + /* GCC in C99 mode treats %a as the C99 format expecting float *, + but glibc with _GNU_SOURCE treats %as as the GNU allocation + extension, so resulting in "warning: format '%a' expects argument + of type 'float *', but argument 3 has type 'char **'". This + applies to the other %as, %aS and %a[] formats below as well. */ + DIAG_PUSH_NEEDS_COMMENT; + DIAG_IGNORE_NEEDS_COMMENT (4.9, "-Wformat"); int r = sscanf (buf, "%as", &str); + DIAG_POP_NEEDS_COMMENT; printf ("%d %p\n", r, str); return r != -1 || str != NULL; diff --git a/stdio-common/scanf14.c b/stdio-common/scanf14.c index 6ca5c7c5679632a3..cffccb0b19d2927b 100644 --- a/stdio-common/scanf14.c +++ b/stdio-common/scanf14.c @@ -2,6 +2,7 @@ #include #include #include +#include #define FAIL() \ do { \ @@ -23,6 +24,13 @@ main (void) FAIL (); else if (f != 0.25 || memcmp (c, "s x", 3) != 0) FAIL (); + /* GCC in C99 mode treats %a as the C99 format expecting float *, + but glibc with _GNU_SOURCE treats %as as the GNU allocation + extension, so resulting in "warning: format '%a' expects argument + of type 'float *', but argument 3 has type 'char **'". This + applies to the other %as, %aS and %a[] formats below as well. */ + DIAG_PUSH_NEEDS_COMMENT; + DIAG_IGNORE_NEEDS_COMMENT (4.9, "-Wformat"); if (sscanf (" 1.25s x", "%as%2c", &sp, c) != 2) FAIL (); else @@ -32,10 +40,14 @@ main (void) memset (sp, 'x', sizeof "1.25s"); free (sp); } + DIAG_POP_NEEDS_COMMENT; if (sscanf (" 2.25s x", "%las%2c", &d, c) != 2) FAIL (); else if (d != 2.25 || memcmp (c, " x", 2) != 0) FAIL (); + /* See explanation above. */ + DIAG_PUSH_NEEDS_COMMENT; + DIAG_IGNORE_NEEDS_COMMENT (4.9, "-Wformat"); if (sscanf (" 3.25S x", "%4aS%3c", &lsp, c) != 2) FAIL (); else @@ -54,6 +66,7 @@ main (void) memset (sp, 'x', sizeof "4.25"); free (sp); } + DIAG_POP_NEEDS_COMMENT; if (sscanf ("5.25[0-9.] x", "%la[0-9.]%2c", &d, c) != 2) FAIL (); else if (d != 5.25 || memcmp (c, " x", 2) != 0) @@ -82,6 +95,9 @@ main (void) FAIL (); if (fseek (fp, 0, SEEK_SET) != 0) FAIL (); + /* See explanation above. */ + DIAG_PUSH_NEEDS_COMMENT; + DIAG_IGNORE_NEEDS_COMMENT (4.9, "-Wformat"); if (fscanf (fp, "%as%2c", &sp, c) != 2) FAIL (); else @@ -91,11 +107,15 @@ main (void) memset (sp, 'x', sizeof "1.25s"); free (sp); } + DIAG_POP_NEEDS_COMMENT; if (freopen (fname, "r", stdin) == NULL) FAIL (); else { + /* See explanation above. */ + DIAG_PUSH_NEEDS_COMMENT; + DIAG_IGNORE_NEEDS_COMMENT (4.9, "-Wformat"); if (scanf ("%as%2c", &sp, c) != 2) FAIL (); else @@ -105,6 +125,7 @@ main (void) memset (sp, 'x', sizeof "1.25s"); free (sp); } + DIAG_POP_NEEDS_COMMENT; } fclose (fp);