Patchwork [CPP] Add pragmas for emitting diagnostics

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Submitter Florian Weimer
Date Sept. 25, 2012, 2:25 p.m.
Message ID <5061BEC4.7080506@redhat.com>
Download mbox | patch
Permalink /patch/186825/
State New
Headers show

Comments

Florian Weimer - Sept. 25, 2012, 2:25 p.m.
This patch adds support for #pragma GCC warning and #pragma GCC error. 
These pragmas can be used from preprocessor macros, unlike the existing 
#warning and #error directives.  Library authors can use these pragmas 
to add deprecation warnings to macros they define.

Bootstrapped and tested on x86_64-redhat-linux-gnu, with no apparent 
regressions.  Okay for trunk?
Basile Starynkevitch - Sept. 26, 2012, 3:41 p.m.
On Tue, Sep 25, 2012 at 04:25:08PM +0200, Florian Weimer wrote:
> This patch adds support for #pragma GCC warning and #pragma GCC
> error. These pragmas can be used from preprocessor macros, unlike
> the existing #warning and #error directives.  Library authors can
> use these pragmas to add deprecation warnings to macros they define.
> 
> Bootstrapped and tested on x86_64-redhat-linux-gnu, with no apparent
> regressions.  Okay for trunk?


I can't approve your patch, but I find it useful and wish it would be accepted.

Cheers.
Tom Tromey - Sept. 26, 2012, 8:19 p.m.
>>>>> "Florian" == Florian Weimer <fweimer@redhat.com> writes:

Florian> This patch adds support for #pragma GCC warning and #pragma GCC
Florian> error. These pragmas can be used from preprocessor macros,
Florian> unlike the existing #warning and #error directives.  Library
Florian> authors can use these pragmas to add deprecation warnings to
Florian> macros they define.

I'm not sure if my libcpp review powers extend to an extension like
this.

It seems reasonable to me though.

Florian> Index: gcc/doc/cpp.texi
[...]
Florian> +contained in the pragma must be a single string literal.  Similary,

Typo, "similarly" -- missing "l".

Florian> +@code{#pragma GCC error "message"} issues an error message.  Unlike
Florian> +the @samp{#warning} and @samp{#error} directives provided by
Florian> +compilers, these pragmas can be embedded in preprocessor macros using

I would just remove "provided by compilers".

Florian> +      cpp_error (pfile, CPP_DL_ERROR, "invalid #pragma GCC %s directive",

It seems to me that the '#pragma GCC %s' part should have quotes around
it.

Tom
Robert Dewar - Sept. 26, 2012, 8:55 p.m.
On 9/26/2012 4:19 PM, Tom Tromey wrote:
>>>>>> "Florian" == Florian Weimer <fweimer@redhat.com> writes:
>
> Florian> This patch adds support for #pragma GCC warning and #pragma GCC
> Florian> error. These pragmas can be used from preprocessor macros,
> Florian> unlike the existing #warning and #error directives.  Library
> Florian> authors can use these pragmas to add deprecation warnings to
> Florian> macros they define.
>
> I'm not sure if my libcpp review powers extend to an extension like
> this.
>
> It seems reasonable to me though.

To me too, these correspond to the Compile_Time_Warning and 
Compile_Time_Error in Ada, and are definitely very useful!
Florian Weimer - Sept. 27, 2012, 9:34 a.m.
On 09/26/2012 10:19 PM, Tom Tromey wrote:
>>>>>> "Florian" == Florian Weimer <fweimer@redhat.com> writes:
>
> Florian> This patch adds support for #pragma GCC warning and #pragma GCC
> Florian> error. These pragmas can be used from preprocessor macros,
> Florian> unlike the existing #warning and #error directives.  Library
> Florian> authors can use these pragmas to add deprecation warnings to
> Florian> macros they define.
>
> I'm not sure if my libcpp review powers extend to an extension like
> this.
>
> It seems reasonable to me though.

Thanks, I'll wait until next week for further feedback.

> Florian> Index: gcc/doc/cpp.texi
> [...]
> Florian> +contained in the pragma must be a single string literal.  Similary,
>
> Typo, "similarly" -- missing "l".

Thanks, fixed in my copy.

> Florian> +@code{#pragma GCC error "message"} issues an error message.  Unlike
> Florian> +the @samp{#warning} and @samp{#error} directives provided by
> Florian> +compilers, these pragmas can be embedded in preprocessor macros using
>
> I would just remove "provided by compilers".

Yes, it's a bit awkward, and I've removed it.  I wanted to stress that 
these directives aren't part of the preprocessor, to avoid confusion.

> Florian> +      cpp_error (pfile, CPP_DL_ERROR, "invalid #pragma GCC %s directive",
>
> It seems to me that the '#pragma GCC %s' part should have quotes around
> it.

Good.  I don't think we've got the magic quotes inside libgcc, so I'm 
just going with this, following other examples in the file:

+      cpp_error (pfile, CPP_DL_ERROR, "invalid \"#pragma GCC %s\" 
directive",
+		 error ? "error" : "warning");

Patch

gcc/ChangeLog:

2012-09-25  Florian Weimer  <fweimer@redhat.com>

	* doc/cpp.texi (Pragmas): Document #pragma GCC warning, #pragma
	GCC error.

gcc/testsuite/ChangeLog:

2012-09-25  Florian Weimer  <fweimer@redhat.com>

	* c-c++-common/cpp/diagnostic-pragma-1.c: New testcase.

libcpp/ChangeLog:

2012-09-25  Florian Weimer  <fweimer@redhat.com>

	* directives.c (do_pragma_warning_or_error): New.
	(do_pragma_warning): New.
	(do_pragma_error): New.
	(_cpp_init_internal_pragmas): Register new pragmas.

Index: gcc/doc/cpp.texi
===================================================================
--- gcc/doc/cpp.texi	(revision 191700)
+++ gcc/doc/cpp.texi	(working copy)
@@ -3634,6 +3634,16 @@ 
 current file to be treated as if it came from a system header.
 @xref{System Headers}.
 
+@item #pragma GCC warning
+@itemx #pragma GCC error
+@code{#pragma GCC warning "message"} causes the preprocessor to issue
+a warning diagnostic with the text @samp{message}.  The message
+contained in the pragma must be a single string literal.  Similary,
+@code{#pragma GCC error "message"} issues an error message.  Unlike
+the @samp{#warning} and @samp{#error} directives provided by
+compilers, these pragmas can be embedded in preprocessor macros using
+@samp{_Pragma}.
+
 @end ftable
 
 @node Other Directives
Index: gcc/testsuite/c-c++-common/cpp/diagnostic-pragma-1.c
===================================================================
--- gcc/testsuite/c-c++-common/cpp/diagnostic-pragma-1.c	(revision 0)
+++ gcc/testsuite/c-c++-common/cpp/diagnostic-pragma-1.c	(working copy)
@@ -0,0 +1,11 @@ 
+// { dg-do compile }
+
+#pragma GCC warning "warn-a" // { dg-warning warn-a }
+#pragma GCC error "err-b" // { dg-error err-b }
+
+#define CONST1 _Pragma("GCC warning \"warn-c\"") 1
+#define CONST2 _Pragma("GCC error \"err-d\"") 2
+
+char a[CONST1]; // { dg-warning warn-c }
+char b[CONST2]; // { dg-error err-d }
+
Index: libcpp/directives.c
===================================================================
--- libcpp/directives.c	(revision 191700)
+++ libcpp/directives.c	(working copy)
@@ -1,7 +1,5 @@ 
 /* CPP Library. (Directive handling.)
-   Copyright (C) 1986, 1987, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
-   1999, 2000, 2001, 2002, 2003, 2004, 2005,
-   2007, 2008, 2009, 2010, 2011 Free Software Foundation, Inc.
+   Copyright (C) 1986-2012 Free Software Foundation, Inc.
    Contributed by Per Bothner, 1994-95.
    Based on CCCP program by Paul Rubin, June 1986
    Adapted to ANSI C, Richard Stallman, Jan 1987
@@ -118,6 +116,9 @@ 
 static void do_pragma_poison (cpp_reader *);
 static void do_pragma_system_header (cpp_reader *);
 static void do_pragma_dependency (cpp_reader *);
+static void do_pragma_warning_or_error (cpp_reader *, bool error);
+static void do_pragma_warning (cpp_reader *);
+static void do_pragma_error (cpp_reader *);
 static void do_linemarker (cpp_reader *);
 static const cpp_token *get_token_no_padding (cpp_reader *);
 static const cpp_token *get__Pragma_string (cpp_reader *);
@@ -1263,6 +1264,8 @@ 
   register_pragma_internal (pfile, "GCC", "system_header",
 			    do_pragma_system_header);
   register_pragma_internal (pfile, "GCC", "dependency", do_pragma_dependency);
+  register_pragma_internal (pfile, "GCC", "warning", do_pragma_warning);
+  register_pragma_internal (pfile, "GCC", "error", do_pragma_error);
 }
 
 /* Return the number of registered pragmas in PE.  */
@@ -1634,6 +1637,42 @@ 
   free ((void *) fname);
 }
 
+/* Issue a diagnostic with the message taken from the pragma.  If
+   ERROR is true, the diagnostic is a warning, otherwise, it is an
+   error.  */
+static void
+do_pragma_warning_or_error (cpp_reader *pfile, bool error)
+{
+  const cpp_token *tok = _cpp_lex_token (pfile);
+  cpp_string str;
+  if (tok->type != CPP_STRING
+      || !cpp_interpret_string_notranslate (pfile, &tok->val.str, 1, &str,
+					    CPP_STRING)
+      || str.len == 0)
+    {
+      cpp_error (pfile, CPP_DL_ERROR, "invalid #pragma GCC %s directive",
+		 error ? "error" : "warning");
+      return;
+    }
+  cpp_error (pfile, error ? CPP_DL_ERROR : CPP_DL_WARNING,
+	     "%s", str.text);
+  free ((void *)str.text);
+}
+
+/* Issue a warning diagnostic.  */
+static void
+do_pragma_warning (cpp_reader *pfile)
+{
+  do_pragma_warning_or_error (pfile, false);
+}
+
+/* Issue an error diagnostic.  */
+static void
+do_pragma_error (cpp_reader *pfile)
+{
+  do_pragma_warning_or_error (pfile, true);
+}
+
 /* Get a token but skip padding.  */
 static const cpp_token *
 get_token_no_padding (cpp_reader *pfile)