Re: RFA: PATCH to use -std=c++98 in stage 1 of bootstrap

[Jason Merrill <jason at redhat dot com>]

On 05/20/2015 06:11 PM, Alexandre Oliva wrote:
> The only serious problem with the patch is that it changes Makefile.in,
> but not the corresponding part of Makefile.tpl from which it is
> generated.  Ok with that change.
>
> Now, if you'd also update the comments just before it, that still
> suggest we build only C in stage1, that would be appreciated.

Sure, here's what I'm applying.


commit 09fbb5f79eae1e95ce64b0f746e9085567e86fbf
Author: Jason Merrill <jason@redhat.com>
Date:   Mon May 18 23:58:41 2015 -0400

    	* configure.ac: Add -std=c++98 to stage1_cxxflags.
    	* Makefile.tpl (STAGE1_CXXFLAGS): And substitute it.
    	* Makefile.in, configure: Regenerate.

diff --git a/Makefile.in b/Makefile.in
index c221a0b..7ae2a40 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -482,13 +482,12 @@ STAGEfeedback_TFLAGS = $(STAGE_TFLAGS)
 STAGEfeedback_CONFIGURE_FLAGS = $(STAGE_CONFIGURE_FLAGS)
 
 
-# Only build the C compiler for stage1, because that is the only one that
-# we can guarantee will build with the native compiler, and also it is the
-# only thing useful for building stage2. STAGE1_CFLAGS (via CFLAGS),
-# MAKEINFO and MAKEINFOFLAGS are explicitly passed here to make them
-# overrideable (for a bootstrap build stage1 also builds gcc.info).
+# By default, C and C++ are the only stage1 languages, because they are the
+# only ones we require to build with the bootstrap compiler, and also the
+# only ones useful for building stage2.
 
 STAGE1_CFLAGS = @stage1_cflags@
+STAGE1_CXXFLAGS = @stage1_cxxflags@
 STAGE1_CHECKING = @stage1_checking@
 STAGE1_LANGUAGES = @stage1_languages@
 # * We force-disable intermodule optimizations, even if
@@ -677,7 +676,9 @@ CXX_FOR_TARGET_FLAG_TO_PASS = \
 	$(shell if echo "$(CXX_FOR_TARGET)" | grep " -funconfigured-" > /dev/null; then :; else echo '"CXX_FOR_TARGET=$(CXX_FOR_TARGET)"'; fi)
 @endif target-libstdc++-v3
 
-# Flags to pass down to all sub-makes.
+# Flags to pass down to all sub-makes. STAGE*FLAGS,
+# MAKEINFO and MAKEINFOFLAGS are explicitly passed here to make them
+# overrideable (for a bootstrap build stage1 also builds gcc.info).
 BASE_FLAGS_TO_PASS = \
 	"DESTDIR=$(DESTDIR)" \
 	"RPATH_ENVVAR=$(RPATH_ENVVAR)" \
diff --git a/Makefile.tpl b/Makefile.tpl
index ec53b59..914196f 100644
--- a/Makefile.tpl
+++ b/Makefile.tpl
@@ -435,13 +435,12 @@ STAGE[+id+]_TFLAGS = $(STAGE_TFLAGS)
 STAGE[+id+]_CONFIGURE_FLAGS = $(STAGE_CONFIGURE_FLAGS)
 [+ ENDFOR bootstrap-stage +]
 
-# Only build the C compiler for stage1, because that is the only one that
-# we can guarantee will build with the native compiler, and also it is the
-# only thing useful for building stage2. STAGE1_CFLAGS (via CFLAGS),
-# MAKEINFO and MAKEINFOFLAGS are explicitly passed here to make them
-# overrideable (for a bootstrap build stage1 also builds gcc.info).
+# By default, C and C++ are the only stage1 languages, because they are the
+# only ones we require to build with the bootstrap compiler, and also the
+# only ones useful for building stage2.
 
 STAGE1_CFLAGS = @stage1_cflags@
+STAGE1_CXXFLAGS = @stage1_cxxflags@
 STAGE1_CHECKING = @stage1_checking@
 STAGE1_LANGUAGES = @stage1_languages@
 # * We force-disable intermodule optimizations, even if
@@ -579,7 +578,9 @@ CXX_FOR_TARGET_FLAG_TO_PASS = \
 	$(shell if echo "$(CXX_FOR_TARGET)" | grep " -funconfigured-" > /dev/null; then :; else echo '"CXX_FOR_TARGET=$(CXX_FOR_TARGET)"'; fi)
 @endif target-libstdc++-v3
 
-# Flags to pass down to all sub-makes.
+# Flags to pass down to all sub-makes. STAGE*FLAGS,
+# MAKEINFO and MAKEINFOFLAGS are explicitly passed here to make them
+# overrideable (for a bootstrap build stage1 also builds gcc.info).
 BASE_FLAGS_TO_PASS =[+ FOR flags_to_pass +][+ IF optional +] \
 	"`echo '[+flag+]=$([+flag+])' | sed -e s'/[^=][^=]*=$$/XFOO=/'`"[+ ELSE optional +] \
 	"[+flag+]=$([+flag+])"[+ ENDIF optional+][+ ENDFOR flags_to_pass +][+ FOR bootstrap-stage +] \
diff --git a/configure b/configure
index d804329..07aba3e 100755
--- a/configure
+++ b/configure
@@ -559,6 +559,7 @@ compare_exclusions
 host_shared
 stage2_werror_flag
 stage1_checking
+stage1_cxxflags
 stage1_cflags
 MAINT
 MAINTAINER_MODE_FALSE
@@ -14755,6 +14756,13 @@ case $build in
       *) stage1_cflags="-g -J" ;;
     esac ;;
 esac
+stage1_cxxflags='$(STAGE1_CFLAGS)'
+if test "$GCC" = yes; then
+  # Build stage 1 in C++98 mode to ensure that a C++98 compiler can still
+  # start the bootstrap.
+  stage1_cxxflags="$stage1_cxxflags -std=c++98"
+fi
+
 
 
 
diff --git a/configure.ac b/configure.ac
index 4da04b7..5808eda 100644
--- a/configure.ac
+++ b/configure.ac
@@ -3476,8 +3476,15 @@ case $build in
       *) stage1_cflags="-g -J" ;;
     esac ;;
 esac
+stage1_cxxflags='$(STAGE1_CFLAGS)'
+if test "$GCC" = yes; then
+  # Build stage 1 in C++98 mode to ensure that a C++98 compiler can still
+  # start the bootstrap.
+  stage1_cxxflags="$stage1_cxxflags -std=c++98"
+fi
 
 AC_SUBST(stage1_cflags)
+AC_SUBST(stage1_cxxflags)
 
 # Enable --enable-checking in stage1 of the compiler.
 AC_ARG_ENABLE(stage1-checking,