Re: Desire gcc option to skip warnings in standard headers

[Branko Cibej <branko dot cibej at hermes dot si>]

Jeffrey A Law wrote:

>   > That's trivial to do, of course -- most probably I should just invert the
>   > meaning of the option. What about the name of the option, though? I don't like
>   > -W(no-)system-headers, even though I thought it up myself...
> Warnings should be enabled by -W<foo> and disabled by -Wno-<foo>.  I'm
> not aware of any that do not follow that convention and I don't think we
> should start making any now :-)
>
> The default behavior can either be on or off, that's separate from
> making -W<foo> and -Wno-<foo> do the right thing.

Right. The attached patches don't change the default behaviour, but inhibit warnings
from system headers if -Wno-system-headers. The patch for cpplib is separate because I
haven't really tested it -- I'd have to reconfigure the compiler. BTW, the patches are
against the latest snapshot.

--
Branko Cibej   <branko.cibej@hermes.si>
HERMES SoftLab, Litijska 51, 1000 Ljubljana, Slovenia
phone: (++386 61) 186 53 49  fax: (++386 61) 186 52 70

1998-06-30  Branko Cibej  <branko.cibej@hermes.si>

	* flags.h: New extern declaration warn_system_headers.
	
	* toplev.c: New warning flag warn_system_headers.
	(W_options): Added initialisation for warn_system_headers.
	(count_error): Inhibit warninhs from system headers if
	warn_system_headers is 0.

	* cccp.c: New warning flag warn_system_headers.
	(INHIBIT_WARNINGS): New predicate, checks if warnings may be
	printed.
	(main): Handle option `-Wsystem-headers'.
	(vwarning, vwarning_with_line, pedwarn_with_file_and_line):
	Use INHIBIT_WARNINGS instead of flag inhibit_warnings.

	* cpplib.h (CPP_INHIBIT_WARNINGS): New predicate, checks if
	warnings may be printed.
	(cpp_options): New member warn_system_headers.

	* cpplib.c (cpp_options_init): Initialise member
	warn_system_headers.
	(cpp_handle_option): Handle option `-Wsystem-headers'.
	(v_cpp_warning, v_cpp_warning_with_line,
	cpp_pedwarn_with_file_and_line): Use CPP_INHIBIT_WARNINGS instead
	of flag inhibit_warnings.

Index: gcc/flags.h
===================================================================
RCS file: /egcs/carton/cvsfiles/egcs/gcc/flags.h,v
retrieving revision 1.16
diff -p -r1.16 flags.h
*** flags.h	1998/06/25 15:14:16	1.16
--- flags.h	1998/06/30 07:41:27
*************** extern unsigned larger_than_size;
*** 137,142 ****
--- 137,146 ----
  
  extern int warn_aggregate_return;
  
+ /* Print warnings generated in system headers */
+ 
+ extern int warn_system_headers;
+ 
  /* Nonzero if generating code to do profiling.  */
  
  extern int profile_flag;
Index: gcc/toplev.c
===================================================================
RCS file: /egcs/carton/cvsfiles/egcs/gcc/toplev.c,v
retrieving revision 1.79
diff -p -r1.79 toplev.c
*** toplev.c	1998/06/27 15:51:49	1.79
--- toplev.c	1998/06/30 07:41:29
*************** int warn_inline;
*** 985,990 ****
--- 985,994 ----
  
  int warn_aggregate_return;
  
+ /* Print warnings generated in system headers */
+ 
+ int warn_system_headers = 1;
+ 
  /* Likewise for -W.  */
  
  struct { char *string; int *variable; int on_value;} W_options[] =
*************** struct { char *string; int *variable; in
*** 996,1002 ****
    {"aggregate-return", &warn_aggregate_return, 1},
    {"cast-align", &warn_cast_align, 1},
    {"uninitialized", &warn_uninitialized, 1},
!   {"inline", &warn_inline, 1}
  };
  
  /* Output files for assembler code (real compiler output)
--- 1000,1007 ----
    {"aggregate-return", &warn_aggregate_return, 1},
    {"cast-align", &warn_cast_align, 1},
    {"uninitialized", &warn_uninitialized, 1},
!   {"inline", &warn_inline, 1},
!   {"system-headers", &warn_system_headers, 1}
  };
  
  /* Output files for assembler code (real compiler output)
*************** int
*** 1121,1127 ****
  count_error (warningp)
       int warningp;
  {
!   if (warningp && inhibit_warnings)
      return 0;
  
    if (warningp && !warnings_are_errors)
--- 1126,1133 ----
  count_error (warningp)
       int warningp;
  {
!   if (warningp
!       && (inhibit_warnings || (in_system_header && !warn_system_headers)))
      return 0;
  
    if (warningp && !warnings_are_errors)
Index: gcc/cccp.c
===================================================================
RCS file: /egcs/carton/cvsfiles/egcs/gcc/cccp.c,v
retrieving revision 1.28
diff -p -r1.28 cccp.c
*** cccp.c	1998/06/19 01:34:11	1.28
--- cccp.c	1998/06/30 07:41:32
*************** static int pedantic_errors;
*** 270,275 ****
--- 270,285 ----
  
  static int inhibit_warnings = 0;
  
+ /* Print warnings generated in system headers */
+ 
+ static int warn_system_headers = 1;
+ 
+ /* Predicate to check whether warnings should be emitted */
+ 
+ #define INHIBIT_WARNINGS()   \
+   (inhibit_warnings          \
+    || (instack[indepth].system_header_p && !warn_system_headers))
+ 
  /* Nonzero means warn if slash-star appears in a slash-star comment,
     or if newline-backslash appears in a slash-slash comment.  */
  
*************** main (argc, argv)
*** 1461,1466 ****
--- 1471,1480 ----
  	    warn_trigraphs = 1;
  	    warn_comments = 1;
  	  }
+ 	else if (!strcmp (argv[i], "-Wsystem-headers"))
+ 	  warn_system_headers = 1;
+ 	else if (!strcmp (argv[i], "-Wno-system-headers"))
+ 	  warn_system_headers = 0;
  	break;
  
        case 'M':
*************** vwarning (msg, args)
*** 9003,9009 ****
    int i;
    FILE_BUF *ip = NULL;
  
!   if (inhibit_warnings)
      return;
  
    if (warnings_are_errors)
--- 9017,9023 ----
    int i;
    FILE_BUF *ip = NULL;
  
!   if (INHIBIT_WARNINGS ())
      return;
  
    if (warnings_are_errors)
*************** vwarning_with_line (line, msg, args)
*** 9101,9107 ****
    int i;
    FILE_BUF *ip = NULL;
  
!   if (inhibit_warnings)
      return;
  
    if (warnings_are_errors)
--- 9115,9121 ----
    int i;
    FILE_BUF *ip = NULL;
  
!   if (INHIBIT_WARNINGS ())
      return;
  
    if (warnings_are_errors)
*************** pedwarn_with_file_and_line VPROTO ((char
*** 9185,9191 ****
  #endif
    va_list args;
  
!   if (!pedantic_errors && inhibit_warnings)
      return;
    if (file) {
      eprint_string (file, file_len);
--- 9199,9205 ----
  #endif
    va_list args;
  
!   if (!pedantic_errors && INHIBIT_WARNINGS ())
      return;
    if (file) {
      eprint_string (file, file_len);

Index: gcc/cpplib.h
===================================================================
RCS file: /egcs/carton/cvsfiles/egcs/gcc/cpplib.h,v
retrieving revision 1.7
diff -p -r1.7 cpplib.h
*** cpplib.h	1998/06/23 13:51:33	1.7
--- cpplib.h	1998/06/30 07:41:06
*************** struct cpp_reader {
*** 313,318 ****
--- 313,324 ----
  /* The bottom of the buffer stack. */
  #define CPP_NULL_BUFFER(PFILE) (&(PFILE)->buffer_stack[CPP_STACK_MAX])
  
+ /* Predicate to check whether warnings should be emitted */
+ #define CPP_INHIBIT_WARNINGS(PFILE)                       \
+   (CPP_OPTIONS (PFILE)->inhibit_warnings                  \
+    || (CPP_BUFFER (PFILE)->system_header_p                \
+        && !CPP_OPTIONS (PFILE)->warn_system_headers))
+ 
  /* Pointed to by cpp_reader::data. */
  struct cpp_options {
    char *in_fname;
*************** struct cpp_options {
*** 384,389 ****
--- 390,399 ----
    /* Nonzero means don't print warning messages.  -w.  */
  
    char inhibit_warnings;
+ 
+ /* Print warnings generated in system headers */
+ 
+   char warn_system_headers;
  
    /* Nonzero means warn if slash-star appears in a comment.  */
  
Index: gcc/cpplib.c
===================================================================
RCS file: /egcs/carton/cvsfiles/egcs/gcc/cpplib.c,v
retrieving revision 1.23
diff -p -r1.23 cpplib.c
*** cpplib.c	1998/06/23 13:51:32	1.23
--- cpplib.c	1998/06/30 07:41:08
*************** cpp_options_init (opts)
*** 770,775 ****
--- 770,776 ----
    opts->chill = 0;
    opts->pedantic_errors = 0;
    opts->inhibit_warnings = 0;
+   opts->warn_system_headers = 1;
    opts->warn_comments = 0;
    opts->warn_import = 1;
    opts->warnings_are_errors = 0;
*************** cpp_handle_option (pfile, argc, argv)
*** 6501,6506 ****
--- 6502,6511 ----
  	  opts->warn_trigraphs = 1;
  	  opts->warn_comments = 1;
  	}
+       else if (!strcmp (argv[i], "-Wsystem-headers"))
+ 	opts->warn_system_headers = 1;
+       else if (!strcmp (argv[i], "-Wno-system-headers"))
+ 	opts->warn_system_headers = 0;
        break;
        
      case 'M':
*************** v_cpp_warning (pfile, msg, ap)
*** 7390,7396 ****
    const char *msg;
    va_list ap;
  {
!   if (CPP_OPTIONS (pfile)->inhibit_warnings)
      return;
  
    if (CPP_OPTIONS (pfile)->warnings_are_errors)
--- 7395,7401 ----
    const char *msg;
    va_list ap;
  {
!   if (CPP_INHIBIT_WARNINGS (pfile))
      return;
  
    if (CPP_OPTIONS (pfile)->warnings_are_errors)
*************** v_cpp_warning_with_line (pfile, line, co
*** 7498,7504 ****
  {
    cpp_buffer *ip;
  
!   if (CPP_OPTIONS (pfile)->inhibit_warnings)
      return;
  
    if (CPP_OPTIONS (pfile)->warnings_are_errors)
--- 7503,7509 ----
  {
    cpp_buffer *ip;
  
!   if (CPP_INHIBIT_WARNINGS (pfile))
      return;
  
    if (CPP_OPTIONS (pfile)->warnings_are_errors)
*************** cpp_pedwarn_with_file_and_line VPROTO ((
*** 7591,7597 ****
  #endif
  
    if (!CPP_OPTIONS (pfile)->pedantic_errors
!       && CPP_OPTIONS (pfile)->inhibit_warnings)
      return;
    if (file != NULL)
      cpp_file_line_for_message (pfile, file, line, -1);
--- 7596,7602 ----
  #endif
  
    if (!CPP_OPTIONS (pfile)->pedantic_errors
!       && CPP_INHIBIT_WARNINGS (pfile))
      return;
    if (file != NULL)
      cpp_file_line_for_message (pfile, file, line, -1);