Patchwork Add implicit C linkage for win32-specific entry points

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Submitter Jacek Caban
Date Sept. 12, 2013, 12:49 p.m.
Message ID <5231B851.4050203@gmail.com>
Download mbox | patch
Permalink /patch/274549/
State New
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Comments

Jacek Caban - Sept. 12, 2013, 12:49 p.m.
On 09/12/13 14:38, Jason Merrill wrote:
> On 09/12/2013 06:26 AM, Jacek Caban wrote:
>> +@deftypefn {C Target Hook} bool TARGET_CXX_IMPLICIT_EXTERN_C (const
>> char*@var{})
>> +Define this hook to add target-specific C++ implicit extern C
>> functions. An example of such function is WinMain on Win32 targets.
>> +@end deftypefn
>
> Let's clarify this a bit.  Perhaps add a middle sentence,
>
> If this function returns true for the name of a file-scope function,
> that function implicitly gets extern "C" linkage rather than whatever
> language linkage the declaration would normally have.
>
> OK with that change.

Thanks for review, a patch with that change is attached.

Jacek
commit 2647e6d0a095658829e275a96b63814b488e0451
Author: Jacek Caban <jacek@codeweavers.com>
Date:   Sat Dec 29 18:06:39 2012 +0100

    Add implicit C linkage for win32-specific entry points
    
    gcc/c-family/ChangeLog:
    	c-target.def: New hook
    
    gcc/ChangeLog:
    	config/config.gcc: Use new winnt-c.c target hooks
    	config/t-winnt: New file
    	config/winnt-c.c: New file
    	doc/tm.texi.in: Document new hook
    	doc/tm.texi: Regenerated
    
    gcc/cp/Changelog:
    	decl.c: Use new cxx_implicit_extern_c hook
    
    gcc/testsuite/ChangeLog:
    	g++.dg/abi/main.C: Added implicit C linkage tests
Kai Tietz - Sept. 13, 2013, 6:08 p.m.
Applied at revision 202573.

Thanks,
Kai

Patch

diff --git a/gcc/c-family/c-target.def b/gcc/c-family/c-target.def
index 80042df..925dbd1 100644
--- a/gcc/c-family/c-target.def
+++ b/gcc/c-family/c-target.def
@@ -102,5 +102,15 @@  DEFHOOK
  than just the compiler.",
  const char *, (void),
  hook_constcharptr_void_null)
+
+DEFHOOK
+(cxx_implicit_extern_c,
+ "Define this hook to add target-specific C++ implicit extern C functions.\
+ If this function returns true for the name of a file-scope function, that\
+ function implicitly gets extern \"C\" linkage rather than whatever language\
+ linkage the declaration would normally have.  An example of such function\
+ is WinMain on Win32 targets.",
+ bool, (const char*),
+ NULL)
  
 HOOK_VECTOR_END (C90_EMPTY_HACK)
diff --git a/gcc/config.gcc b/gcc/config.gcc
index 36d5ae8..22f30f4 100644
--- a/gcc/config.gcc
+++ b/gcc/config.gcc
@@ -1526,6 +1526,9 @@  x86_64-*-cygwin*)
 i[34567]86-*-mingw* | x86_64-*-mingw*)
 	tm_file="${tm_file} i386/unix.h i386/bsd.h i386/gas.h dbxcoff.h i386/cygming.h"
 	xm_file=i386/xm-mingw32.h
+	c_target_objs="${c_target_objs} winnt-c.o"
+	cxx_target_objs="${cxx_target_objs} winnt-c.o"
+	target_has_targetcm="yes"
 	case ${target} in
 		x86_64-*-* | *-w64-*)
 			need_64bit_isa=yes
@@ -1565,7 +1568,7 @@  i[34567]86-*-mingw* | x86_64-*-mingw*)
 			;;
 	esac
 	tm_file="${tm_file} i386/mingw-stdint.h"
-	tmake_file="${tmake_file} i386/t-cygming t-slibgcc"
+	tmake_file="${tmake_file} t-winnt i386/t-cygming t-slibgcc"
         case ${target} in
                x86_64-w64-*)
                		tmake_file="${tmake_file} i386/t-mingw-w64"
diff --git a/gcc/config/t-winnt b/gcc/config/t-winnt
new file mode 100644
index 0000000..1751622
--- /dev/null
+++ b/gcc/config/t-winnt
@@ -0,0 +1,22 @@ 
+# Copyright (C) 2013 Free Software Foundation, Inc.
+#
+# This file is part of GCC.
+#
+# GCC is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3, or (at your option)
+# any later version.
+#
+# GCC is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with GCC; see the file COPYING3.  If not see
+# <http://www.gnu.org/licenses/>.
+
+winnt-c.o: config/winnt-c.c $(CONFIG_H) $(SYSTEM_H) coretypes.h \
+  $(C_TARGET_H) $(C_TARGET_DEF_H)
+	$(COMPILER) -c $(ALL_COMPILERFLAGS) $(ALL_CPPFLAGS) \
+	  $< $(OUTPUT_OPTION)
diff --git a/gcc/config/winnt-c.c b/gcc/config/winnt-c.c
new file mode 100644
index 0000000..d52db62
--- /dev/null
+++ b/gcc/config/winnt-c.c
@@ -0,0 +1,39 @@ 
+/* Default C-family target hooks initializer.
+   Copyright (C) 2013
+   Free Software Foundation, Inc.
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free
+Software Foundation; either version 3, or (at your option) any later
+version.
+
+GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+#include "config.h"
+#include "system.h"
+#include "coretypes.h"
+#include "c-family/c-target.h"
+#include "c-family/c-target-def.h"
+
+static bool
+winnt_implicit_extern_c (const char *ident)
+{
+  return !strcmp(ident, "wmain")
+      || !strcmp(ident, "DllMain")
+      || !strcmp(ident, "WinMain")
+      || !strcmp(ident, "wWinMain");
+}
+
+#undef TARGET_CXX_IMPLICIT_EXTERN_C
+#define TARGET_CXX_IMPLICIT_EXTERN_C winnt_implicit_extern_c
+
+struct gcc_targetcm targetcm = TARGETCM_INITIALIZER;
diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index b4223aa..f193676 100644
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -44,6 +44,7 @@  along with GCC; see the file COPYING3.  If not see
 #include "c-family/c-common.h"
 #include "c-family/c-objc.h"
 #include "c-family/c-pragma.h"
+#include "c-family/c-target.h"
 #include "diagnostic.h"
 #include "intl.h"
 #include "debug.h"
@@ -7457,7 +7458,9 @@  grokfndecl (tree ctype,
        || (IDENTIFIER_LENGTH (declarator) > 10
 	   && IDENTIFIER_POINTER (declarator)[0] == '_'
 	   && IDENTIFIER_POINTER (declarator)[1] == '_'
-	   && strncmp (IDENTIFIER_POINTER (declarator)+2, "builtin_", 8) == 0))
+	   && strncmp (IDENTIFIER_POINTER (declarator)+2, "builtin_", 8) == 0)
+       || (targetcm.cxx_implicit_extern_c
+	   && targetcm.cxx_implicit_extern_c(IDENTIFIER_POINTER (declarator))))
       && current_lang_name == lang_name_cplusplus
       && ctype == NULL_TREE
       && DECL_FILE_SCOPE_P (decl))
diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
index d15f53c..a7ab95a 100644
--- a/gcc/doc/tm.texi
+++ b/gcc/doc/tm.texi
@@ -10651,6 +10651,10 @@  Define this hook to return the name of a header file to be included at the start
  This hook can be used together with a header provided by the system C library to implement ISO C requirements for certain macros to be predefined that describe properties of the whole implementation rather than just the compiler.
 @end deftypefn
 
+@deftypefn {C Target Hook} bool TARGET_CXX_IMPLICIT_EXTERN_C (const char*@var{})
+Define this hook to add target-specific C++ implicit extern C functions. If this function returns true for the name of a file-scope function, that function implicitly gets extern "C" linkage rather than whatever language linkage the declaration would normally have.  An example of such function is WinMain on Win32 targets.
+@end deftypefn
+
 @defmac NO_IMPLICIT_EXTERN_C
 Define this macro if the system header files support C++ as well as C@.
 This macro inhibits the usual method of using system header files in
diff --git a/gcc/doc/tm.texi.in b/gcc/doc/tm.texi.in
index b51d7b3..fdc3925 100644
--- a/gcc/doc/tm.texi.in
+++ b/gcc/doc/tm.texi.in
@@ -7985,6 +7985,8 @@  files @code{__STDC__} will always expand to 1.
 
 @hook TARGET_C_PREINCLUDE
 
+@hook TARGET_CXX_IMPLICIT_EXTERN_C
+
 @defmac NO_IMPLICIT_EXTERN_C
 Define this macro if the system header files support C++ as well as C@.
 This macro inhibits the usual method of using system header files in
diff --git a/gcc/testsuite/g++.dg/abi/main.C b/gcc/testsuite/g++.dg/abi/main.C
new file mode 100644
index 0000000..4c5f1ea
--- /dev/null
+++ b/gcc/testsuite/g++.dg/abi/main.C
@@ -0,0 +1,24 @@ 
+/* { dg-do compile } */
+
+/* Check if entry points get implicit C linkage. If they don't, compiler will
+ * error on incompatible declarations */
+
+int main();
+extern "C" int main();
+
+#ifdef __MINGW32__
+
+int wmain();
+extern "C" int wmain();
+
+int DllMain();
+extern "C" int DllMain();
+
+int WinMain();
+extern "C" int WinMain();
+
+int wWinMain();
+extern "C" int wWinMain();
+
+#endif
+