diff mbox series

gcc, libcpp: Add warning switch for "#pragma once in main file" [PR89808]

Message ID 20240302064520.2076664-1-kmatsui@gcc.gnu.org
State New
Headers show
Series gcc, libcpp: Add warning switch for "#pragma once in main file" [PR89808] | expand

Commit Message

Ken Matsui March 2, 2024, 6:45 a.m. UTC 
This patch adds a warning switch for "#pragma once in main file".  The
warning option name is Wpragma-once-outside-header, which is the same
as Clang.

	PR preprocessor/89808

gcc/c-family/ChangeLog:

	* c-opts.cc (c_common_handle_option): Handle
	OPT_Wpragma_once_outside_header.
	* c.opt (Wpragma_once_outside_header): Define new option.

gcc/ChangeLog:

	* doc/invoke.texi (Warning Options): Document
	-Wno-pragma-once-outside-header.

libcpp/ChangeLog:

	* include/cpplib.h (struct cpp_options): Define
	cpp_warn_pragma_once_outside_header.
	(enum cpp_warning_reason): Define
	CPP_W_PRAGMA_ONCE_OUTSIDE_HEADER.
	* directives.cc (do_pragma_once): Use
	cpp_warn_pragma_once_outside_header.
	* init.cc (cpp_create_reader): Handle
	cpp_warn_pragma_once_outside_header.

gcc/testsuite/ChangeLog:

	* g++.dg/Wpragma-once-outside-header.C: New test.
	* g++.dg/warn/Wno-pragma-once-outside-header.C: New test.
	* g++.dg/warn/Wpragma-once-outside-header.C: New test.

Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
---
 gcc/c-family/c-opts.cc                                 |  4 ++++
 gcc/c-family/c.opt                                     |  4 ++++
 gcc/doc/invoke.texi                                    | 10 ++++++++--
 gcc/testsuite/g++.dg/Wpragma-once-outside-header.C     |  6 ++++++
 .../g++.dg/warn/Wno-pragma-once-outside-header.C       |  5 +++++
 .../g++.dg/warn/Wpragma-once-outside-header.C          |  6 ++++++
 libcpp/directives.cc                                   |  6 ++++--
 libcpp/include/cpplib.h                                |  6 +++++-
 libcpp/init.cc                                         |  1 +
 9 files changed, 43 insertions(+), 5 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/Wpragma-once-outside-header.C
 create mode 100644 gcc/testsuite/g++.dg/warn/Wno-pragma-once-outside-header.C
 create mode 100644 gcc/testsuite/g++.dg/warn/Wpragma-once-outside-header.C
diff mbox series

Patch

diff --git a/gcc/c-family/c-opts.cc b/gcc/c-family/c-opts.cc
index be3058dca63..2868748a020 100644
--- a/gcc/c-family/c-opts.cc
+++ b/gcc/c-family/c-opts.cc
@@ -430,6 +430,10 @@  c_common_handle_option (size_t scode, const char *arg, HOST_WIDE_INT value,
       cpp_opts->warn_num_sign_change = value;
       break;
 
+    case OPT_Wpragma_once_outside_header:
+      cpp_opts->cpp_warn_pragma_once_outside_header = value;
+      break;
+
     case OPT_Wunknown_pragmas:
       /* Set to greater than 1, so that even unknown pragmas in
 	 system headers will be warned about.  */
diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt
index b7a4a1a68e3..6841a5a5e81 100644
--- a/gcc/c-family/c.opt
+++ b/gcc/c-family/c.opt
@@ -1180,6 +1180,10 @@  Wpragmas
 C ObjC C++ ObjC++ Var(warn_pragmas) Init(1) Warning
 Warn about misuses of pragmas.
 
+Wpragma-once-outside-header
+C ObjC C++ ObjC++ Var(warn_pragma_once_outside_header) Init(1) Warning
+Warn about #pragma once outside of a header.
+
 Wprio-ctor-dtor
 C ObjC C++ ObjC++ Var(warn_prio_ctor_dtor) Init(1) Warning
 Warn if constructor or destructors with priorities from 0 to 100 are used.
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index bdf05be387d..eeb8954bcdf 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -391,8 +391,8 @@  Objective-C and Objective-C++ Dialects}.
 -Wpacked  -Wno-packed-bitfield-compat  -Wpacked-not-aligned  -Wpadded
 -Wparentheses  -Wno-pedantic-ms-format
 -Wpointer-arith  -Wno-pointer-compare  -Wno-pointer-to-int-cast
--Wno-pragmas  -Wno-prio-ctor-dtor  -Wredundant-decls
--Wrestrict  -Wno-return-local-addr  -Wreturn-type
+-Wno-pragmas  -Wno-pragma-once-outside-header  -Wno-prio-ctor-dtor
+-Wredundant-decls  -Wrestrict  -Wno-return-local-addr  -Wreturn-type
 -Wno-scalar-storage-order  -Wsequence-point
 -Wshadow  -Wshadow=global  -Wshadow=local  -Wshadow=compatible-local
 -Wno-shadow-ivar
@@ -7955,6 +7955,12 @@  Do not warn about misuses of pragmas, such as incorrect parameters,
 invalid syntax, or conflicts between pragmas.  See also
 @option{-Wunknown-pragmas}.
 
+@opindex Wno-pragma-once-outside-header
+@opindex Wpragma-once-outside-header
+@item -Wno-pragma-once-outside-header
+Do not warn when @code{#pragma once} is used in a file that is not a header
+file, such as a main file.
+
 @opindex Wno-prio-ctor-dtor
 @opindex Wprio-ctor-dtor
 @item -Wno-prio-ctor-dtor
diff --git a/gcc/testsuite/g++.dg/Wpragma-once-outside-header.C b/gcc/testsuite/g++.dg/Wpragma-once-outside-header.C
new file mode 100644
index 00000000000..66b2c862344
--- /dev/null
+++ b/gcc/testsuite/g++.dg/Wpragma-once-outside-header.C
@@ -0,0 +1,6 @@ 
+/* { dg-do assemble  } */
+/* { dg-options "-Werror=pragma-once-outside-header" } */
+/* { dg-message "some warnings being treated as errors" "" {target "*-*-*"} 0 } */
+
+#pragma once  // { dg-error "#pragma once in main file" }
+int main() {}
diff --git a/gcc/testsuite/g++.dg/warn/Wno-pragma-once-outside-header.C b/gcc/testsuite/g++.dg/warn/Wno-pragma-once-outside-header.C
new file mode 100644
index 00000000000..b5be4d25a9d
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wno-pragma-once-outside-header.C
@@ -0,0 +1,5 @@ 
+// { dg-do assemble  }
+// { dg-options "-Wno-pragma-once-outside-header" }
+
+#pragma once
+int main() {}
diff --git a/gcc/testsuite/g++.dg/warn/Wpragma-once-outside-header.C b/gcc/testsuite/g++.dg/warn/Wpragma-once-outside-header.C
new file mode 100644
index 00000000000..324b0638c3f
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wpragma-once-outside-header.C
@@ -0,0 +1,6 @@ 
+// { dg-do assemble  }
+// { dg-options "-Werror=pragma-once-outside-header" }
+// { dg-message "some warnings being treated as errors" "" {target "*-*-*"} 0 }
+
+#pragma once  // { dg-error "#pragma once in main file" }
+int main() {}
diff --git a/libcpp/directives.cc b/libcpp/directives.cc
index 479f8c716e8..cc8f110b66b 100644
--- a/libcpp/directives.cc
+++ b/libcpp/directives.cc
@@ -1588,8 +1588,10 @@  do_pragma (cpp_reader *pfile)
 static void
 do_pragma_once (cpp_reader *pfile)
 {
-  if (_cpp_in_main_source_file (pfile))
-    cpp_error (pfile, CPP_DL_WARNING, "#pragma once in main file");
+  if (CPP_OPTION (pfile, cpp_warn_pragma_once_outside_header)
+      && _cpp_in_main_source_file (pfile))
+    cpp_warning (pfile, CPP_W_PRAGMA_ONCE_OUTSIDE_HEADER,
+		 "#pragma once in main file");
 
   check_eol (pfile, false);
   _cpp_mark_file_once_only (pfile, pfile->buffer->file);
diff --git a/libcpp/include/cpplib.h b/libcpp/include/cpplib.h
index c62374d3192..7cf49fb2f74 100644
--- a/libcpp/include/cpplib.h
+++ b/libcpp/include/cpplib.h
@@ -583,6 +583,9 @@  struct cpp_options
      2 if it should be a pedwarn.  */
   unsigned char cpp_warn_invalid_utf8;
 
+  /* True if libcpp should warn about #pragma once outside of a header.  */
+  bool cpp_warn_pragma_once_outside_header;
+
   /* True if libcpp should warn about invalid forms of delimited or named
      escape sequences.  */
   bool cpp_warn_unicode;
@@ -701,7 +704,8 @@  enum cpp_warning_reason {
   CPP_W_EXPANSION_TO_DEFINED,
   CPP_W_BIDIRECTIONAL,
   CPP_W_INVALID_UTF8,
-  CPP_W_UNICODE
+  CPP_W_UNICODE,
+  CPP_W_PRAGMA_ONCE_OUTSIDE_HEADER
 };
 
 /* Callback for header lookup for HEADER, which is the name of a
diff --git a/libcpp/init.cc b/libcpp/init.cc
index 54fc9236d38..4be1afdb2c2 100644
--- a/libcpp/init.cc
+++ b/libcpp/init.cc
@@ -235,6 +235,7 @@  cpp_create_reader (enum c_lang lang, cpp_hash_table *table,
   CPP_OPTION (pfile, cpp_warn_bidirectional) = bidirectional_unpaired;
   CPP_OPTION (pfile, cpp_warn_invalid_utf8) = 0;
   CPP_OPTION (pfile, cpp_warn_unicode) = 1;
+  CPP_OPTION (pfile, cpp_warn_pragma_once_outside_header) = 1;
   CPP_OPTION (pfile, cpp_input_charset_explicit) = 0;
 
   /* Default CPP arithmetic to something sensible for the host for the