Add --enable-build-with-cxx configure switch

This new option, disabled by default for now, allows specifying
whether to build GDB, GDBserver, and friends with a C++ (98/03)
compiler.

The name of the switch should be familiar to those who followed GCC's
own C++ conversion process.

. Adding -fpermissive to COMPILER in C++ mode (see the new
build-with-cxx.m4 file) makes errors like these be warnings instead:

  gdb/infrun.c:6597:1: error:   initializing argument 1 of ‘void sig_print_info(gdb_signal)’ [-fpermissive]
   sig_print_info (enum gdb_signal oursig)
   ^
  gdb/infrun.c: In function ‘void do_restore_infcall_suspend_state_cleanup(void*)’:
  gdb/infrun.c:7164:39: error: invalid conversion from ‘void*’ to ‘infcall_suspend_state*’ [-fpermissive]
     restore_infcall_suspend_state (state);
				 ^

so that the compiler carries on compiling the file.  -Werror still
catches the warnings, so nothing is lost, only our lifes are made
easier by concentrating on getting other more important things out of
the way first.

There's no way to quiet those warnings.  Until they're all fixed, when
building in C++ mode, -Werror is disabled by default.

. Adding -Wno-narrowing suppresses thousands of instances of this warning:

  gdb/arm-linux-tdep.c:439:1: error: narrowing conversion of ‘-1’ from ‘int’ to ‘ULONGEST {aka long unsigned int}’ inside { } is ill-formed in C++11 [-Werror=narrowing]
  gdb/arm-linux-tdep.c:439:1: error: narrowing conversion of ‘-1l’ from ‘LONGEST {aka long int}’ to ‘ULONGEST {aka long unsigned int}’ inside { } is ill-formed in C++11 [-Werror=narrowing]
  gdb/arm-linux-tdep.c:450:1: error: narrowing conversion of ‘-1’ from ‘int’ to ‘ULONGEST {aka long unsigned int}’ inside { } is ill-formed in C++11 [-Werror=narrowing]

We can defer handling those until we target C++11.


. Adding -Wno-sign-compare suppresses thousands of instances of this warning:

  gdb/linux-record.c:1763:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
	 if (tmpulongest == tdep->fcntl_F_GETLK64)
				  ^


. Adding -Wno-write-strings suppresses thousands of instances of this warning:

  gdb/mi/mi-cmd-var.c: In function ‘void mi_cmd_var_show_attributes(char*, char**, int)’:
  gdb/mi/mi-cmd-var.c:514:12: warning: deprecated conversion from string constant to ‘char*’ [-Wwrite-strings]
       attstr = "editable";
	      ^
  gdb/mi/mi-cmd-var.c:516:12: warning: deprecated conversion from string constant to ‘char*’ [-Wwrite-strings]
       attstr = "noneditable";
	      ^

For now, it's best to hide these warnings from view until we're
'-fpermissive'-clean, and can thus start building with -Werror.
The C compiler has always managed to build working GDBs with these
issues in the code, so a C++ compiler should too.

gdb/ChangeLog:
2015-02-27  Pedro Alves  <palves@redhat.com>

	* Makefile.in (COMPILER): New, get it from autoconf.
	(COMPILE.pre, CC_LD): Use COMPILER.
	(CXX): Get from autoconf instead.
	(CXX_FOR_TARGET): Default to g++ instead of gcc.
	* acinclude.m4: Include build-with-cxx.m4.
	* build-with-cxx.m4: New file.
	* configure.ac: Call AC_PROG_CXX and GDB_AC_BUILD_WITH_CXX.
	Disable -Werror by default if building in C++ mode.
	(build_warnings): Add -Wno-sign-compare, -Wno-write-strings and
	-Wno-narrowing in C++ mode.  Only enable -Wpointer-sign in C mode.
	Run supported-warning-flags tests with the C++ compiler.
	Save/restore CXXFLAGS too.
	* configure: Regenerate.

gdb/gdbserver/ChangeLog:
2015-02-27  Pedro Alves  <palves@redhat.com>

	* Makefile.in (COMPILER): New, get it from autoconf.
	(CXX): Get from autoconf instead.
	(COMPILE.pre): Use COMPILER.
	(CC-LD): Rename to ...
	(CC_LD): ... this.  Use COMPILER.
	(gdbserver$(EXEEXT), gdbreplay$(EXEEXT), $(IPA_LIB)): Adjust.
	(CXX_FOR_TARGET): Default to g++ instead of gcc.
	* acinclude.m4: Include build-with-cxx.m4.
	* configure.ac: Call AC_PROG_CXX and GDB_AC_BUILD_WITH_CXX.
	Disable -Werror by default if building in C++ mode.
	(build_warnings): Add -Wno-sign-compare, -Wno-write-strings and
	-Wno-narrowing in C++ mode. Run supported-warning-flags tests with
	the C++ compiler.  Save/restore CXXFLAGS too.
	* configure: Regenerate.

1 files changed, 10 insertions, 7 deletions

diff --git a/gdb/Makefile.in b/gdb/Makefile.in
index e9f22d6..e837c6f 100644
--- a/gdb/Makefile.in
+++ b/gdb/Makefile.in
@@ -79,12 +79,16 @@ MSGMERGE = msgmerge
 PACKAGE = @PACKAGE@
 CATALOGS = @CATALOGS@
 
+# The name of the compiler to use.
+COMPILER = @COMPILER@
+
 # If you are compiling with GCC, make sure that either 1) You have the
 # fixed include files where GCC can reach them, or 2) You use the
 # -traditional flag.  Otherwise the ioctl calls in inflow.c
 # will be incorrectly compiled.  The "fixincludes" script in the gcc
 # distribution will fix your include files up.
 CC=@CC@
+CXX=@CXX@
 
 # Dependency tracking information.
 DEPMODE = @CCDEPMODE@
@@ -93,7 +97,7 @@ depcomp = $(SHELL) $(srcdir)/../depcomp
 
 # Note that these are overridden by GNU make-specific code below if
 # GNU make is used.  The overrides implement dependency tracking.
-COMPILE.pre = $(CC)
+COMPILE.pre = $(COMPILER)
 COMPILE.post = -c -o $@
 COMPILE = $(COMPILE.pre) $(INTERNAL_CFLAGS) $(COMPILE.post)
 POSTCOMPILE = @true
@@ -123,7 +127,7 @@ MAKEHTMLFLAGS =
 # Set this up with gcc if you have gnu ld and the loader will print out
 # line numbers for undefined references.
 #CC_LD=gcc -static
-CC_LD=$(CC)
+CC_LD=$(COMPILER)
 
 # Where is our "include" directory?  Typically $(srcdir)/../include.
 # This is essentially the header file directory for the library
@@ -762,19 +766,18 @@ CC_FOR_TARGET = ` \
     fi; \
   fi`
 
-CXX = gcc
 CXX_FOR_TARGET = ` \
-  if [ -f $${rootme}/../gcc/xgcc ] ; then \
+  if [ -f $${rootme}/../gcc/xg++ ] ; then \
     if [ -f $${rootme}/../$(target_subdir)newlib/Makefile ] ; then \
-      echo $${rootme}/../gcc/xgcc -B$${rootme}/../gcc/ -idirafter $${rootme}/$(target_subdir)newlib/targ-include -idirafter $${rootsrc}/../$(target_subdir)newlib/libc/include -nostdinc -B$${rootme}/../$(target_subdir)newlib/; \
+      echo $${rootme}/../gcc/xg++ -B$${rootme}/../gcc/ -idirafter $${rootme}/$(target_subdir)newlib/targ-include -idirafter $${rootsrc}/../$(target_subdir)newlib/libc/include -nostdinc -B$${rootme}/../$(target_subdir)newlib/; \
     else \
-      echo $${rootme}/../gcc/xgcc -B$${rootme}/../gcc/; \
+      echo $${rootme}/../gcc/xg++ -B$${rootme}/../gcc/; \
     fi; \
   else \
     if [ "$(host_canonical)" = "$(target_canonical)" ] ; then \
       echo $(CXX); \
     else \
-      t='$(program_transform_name)'; echo gcc | sed -e '' $$t; \
+      t='$(program_transform_name)'; echo g++ | sed -e '' $$t; \
     fi; \
   fi`