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Re: [PATCH v2] [libcc1] Rename C{,P}_COMPILER_NAME and remove triplet from them
- From: Sergio Durigan Junior <sergiodj at redhat dot com>
- To: Pedro Alves <palves at redhat dot com>
- Cc: GDB Patches <gdb-patches at sourceware dot org>, GCC Patches <gcc-patches at gcc dot gnu dot org>, Tom Tromey <tom at tromey dot com>, Keith Seitz <keiths at redhat dot com>, Phil Muldoon <pmuldoon at redhat dot com>, Alexandre Oliva <aoliva at redhat dot com>
- Date: Fri, 15 Sep 2017 00:11:54 -0400
- Subject: Re: [PATCH v2] [libcc1] Rename C{,P}_COMPILER_NAME and remove triplet from them
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Ping.
On Friday, September 01 2017, I wrote:
> On Wednesday, August 23 2017, Pedro Alves wrote:
>
>> On 08/23/2017 05:17 AM, Sergio Durigan Junior wrote:
>>> Hi there,
>>>
>>> This is a series of two patches, one for GDB and one for GCC, which aims
>>> to improve the detection and handling of triplets present on compiler
>>> names. The motivation for this series was mostly the fact that GDB's
>>> "compile" command is broken on Debian unstable, as can be seen here:
>>>
>>> <https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=851146>
>>>
>>> The reason for the failure is the fact that Debian compiles GCC using
>>> the --program-{prefix,suffix} options from configure in order to name
>>> the compiler using the full triplet (i.e., Debian's GCC is not merely
>>> named "gcc", but e.g. "x86_64-linux-gnu-gcc-7"), which end up naming the
>>> C_COMPILER_NAME and CP_COMPILER_NAME defines with the specified prefix
>>> and suffix. Therefore, the regexp being used to match the compiler name
>>> is wrong because it doesn't take into account the fact that the defines
>>> may already contain the triplets.
>>
>> As discussed on IRC, I think the problem is that C_COMPILER_NAME
>> in libcc1 includes the full triplet in the first place. I think
>> that it shouldn't. I think that C_COMPILER_NAME should always
>> be "gcc".
>>
>> The problem is in bootstrapping code, before there's a plugin
>> yet -- i.e.., in the code that libcc1 uses to find the compiler (which
>> then loads a plugin that libcc1 talks with).
>>
>> Please bear with me while I lay down my rationale, so that we're
>> in the same page.
>>
>> C_COMPILER_NAME seems to include the prefix currently in an attempt
>> to support cross debugging, or more generically, --enable-targets=all
>> in gdb, but the whole thing doesn't really work as intended if
>> C_COMPILER_NAME already includes a target prefix.
>>
>> IIUC the libcc1/plugin design, a single "libcc1.so" (what gdb loads,
>> not the libcc1plugin compiler plugin) should work with any compiler in
>> the PATH, in case you have several in the system. E.g., one for
>> each arch.
>>
>> Let me expand.
>>
>> The idea is that gdb always dlopens "libcc1.so", by that name exactly.
>> Usually that'll open the libcc1.so installed in the system, e.g.,
>> "/usr/lib64/libcc1.so", which for convenience was originally built from the
>> same source tree as the systems's compiler was built. You could force gdb to
>> load some other libcc1.so, e.g., by tweaking LD_LIBRARY_PATH of course,
>> but you shouldn't need to.
>>
>> libcc1.so is responsible for finding a compiler that targets the
>> architecture of the inferior that the user is debugging in gdb.
>> E.g., say you're cross debugging for arm-none-eabi, on a
>> x86-64 Fedora host. GDB knows the target inferior's architecture, and passes
>> down to (the system) libcc1 a triplet regex like "arm*-*eabi*" or
>> similar to libcc1,. libcc1 appends "-" + C_COMPILER_NAME to that regex,
>> generating something like "arm*-*eabi*-gcc", and then looks for binaries
>> in PATH that match that regex. When one is found, e.g., "arm-none-eabi-gcc",
>> libcc1 forks/execs that compiler, passing it "-fplugin=libcc1plugin".
>> libcc1 then communicates with that compiler's libcc1plugin plugin
>> via a socket.
>>
>> In this scheme, "libcc1.so", the library that gdb loads, has no
>> target-specific logic at all. It should work with any compiler
>> in the system, for any target/arch. All it does is marshall the gcc/gdb
>> interface between the gcc plugin and gdb, it is not linked against gcc.
>> That boundary is versioned, and ABI-stable. So as long as the
>> libcc1.so that gdb loads understands the same API version of the gcc/gdb
>> interface API as gdb understands, it all should work. (The APIs
>> are always extended keeping backward compatibility.)
>>
>> So in this scheme, having the "C_COMPILER_NAME" macro in libcc1
>> include the target prefix for the --target that the plugin that
>> libcc1 is built along with, seems to serve no real purpose, AFAICT.
>> It's just getting in the way.
>>
>> I.e., something like:
>>
>> "$gdb_specified_triplet_re" + "-" + C_COMPILER_NAME
>>
>> works if C_COMPILER_NAME is exactly "gcc", but not if C_COMPILER_NAME is already:
>>
>> "$whatever_triplet_libcc1_happened_to_be_built_with" + "-gcc"
>>
>> because we end up with:
>>
>> "$gdb_specified_triplet_re" + "-" "$whatever_triplet_libcc1_happened_to_be_built_with" + "-gcc"
>>
>> which is the problem case.
>>
>> In sum, I think the libcc1.so (not the plugin) should _not_ have baked
>> in target awareness, and thus C_COMPILER_NAME should always be "gcc", and
>> then libcc1's regex should be adjusted to also tolerate a suffix in
>> the final compiler binary name regex.
>>
>> WDYT?
>
> As I replied before, I agree with Pedro's rationale here and his idea
> actually makes my initial patch much simpler. By renaming
> C_COMPILER_NAME (and the new CP_COMPILER_NAME) to just "gcc" (or "g++"),
> the Debian bug I was fixing is solved and we don't have to bother with
> breaking compatibility with older gdb's packaged by the distros, because
> they will also keep working with this change.
>
> So I would like to propose this new patch, only for GCC, which makes
> C_COMPILER_NAME and CP_COMPILER_NAME have "gcc" and "g++" as hardcoded
> names, respectively. In the commit log, I intend to include Pedro's
> rationale (above).
>
> What do you guys think of this new version? It doesn't need any GDB
> patch, and works with both Fedora and Debian.
>
> Thanks,
>
> --
> Sergio
> GPG key ID: 237A 54B1 0287 28BF 00EF 31F4 D0EB 7628 65FC 5E36
> Please send encrypted e-mail if possible
> http://sergiodj.net/
>
> libcc1/ChangeLog:
> 2017-09-01 Sergio Durigan Junior <sergiodj@redhat.com>
> Pedro Alves <palves@redhat.com>
>
> * Makefile.am: Remove references to c-compiler-name.h and
> cp-compiler-name.h
> * Makefile.in: Regenerate.
> * compiler-name.hh: New file.
> * libcc1.cc: Don't include c-compiler-name.h. Include
> compiler-name.hh.
> * libcp1.cc: Don't include cp-compiler-name.h. Include
> compiler-name.hh.
>
> diff --git a/libcc1/Makefile.am b/libcc1/Makefile.am
> index 5e61a92a26b..cdba5a50b23 100644
> --- a/libcc1/Makefile.am
> +++ b/libcc1/Makefile.am
> @@ -45,24 +45,6 @@ plugin_LTLIBRARIES = libcc1plugin.la libcp1plugin.la
> cc1lib_LTLIBRARIES = libcc1.la
> endif
>
> -BUILT_SOURCES = c-compiler-name.h cp-compiler-name.h
> -MOSTLYCLEANFILES = c-compiler-name.h cp-compiler-name.h
> -
> -# Put this in a header so we don't run sed for each compilation. This
> -# is also simpler to debug as one can easily see the constant.
> -# FIXME: compute it in configure.ac and output it in config.status, or
> -# introduce timestamp files for some indirection to avoid rebuilding it
> -# every time.
> -c-compiler-name.h: Makefile
> - -rm -f $@T
> - echo "#define C_COMPILER_NAME \"`echo gcc | sed '$(transform)'`\"" > $@T
> - mv $@T $@ # $(SHELL) $(srcdir)/../move-if-change $@T $@
> -
> -cp-compiler-name.h: Makefile
> - -rm -f $@T
> - echo "#define CP_COMPILER_NAME \"`echo g++ | sed '$(transform)'`\"" > $@T
> - mv $@T $@ # $(SHELL) $(srcdir)/../move-if-change $@T $@
> -
> shared_source = callbacks.cc callbacks.hh connection.cc connection.hh \
> marshall.cc marshall.hh rpc.hh status.hh
>
> diff --git a/libcc1/Makefile.in b/libcc1/Makefile.in
> index 54babb02a49..47be10025ad 100644
> --- a/libcc1/Makefile.in
> +++ b/libcc1/Makefile.in
> @@ -307,8 +307,6 @@ plugindir = $(libdir)/gcc/$(target_noncanonical)/$(gcc_version)/plugin
> cc1libdir = $(libdir)/$(libsuffix)
> @ENABLE_PLUGIN_TRUE@plugin_LTLIBRARIES = libcc1plugin.la libcp1plugin.la
> @ENABLE_PLUGIN_TRUE@cc1lib_LTLIBRARIES = libcc1.la
> -BUILT_SOURCES = c-compiler-name.h cp-compiler-name.h
> -MOSTLYCLEANFILES = c-compiler-name.h cp-compiler-name.h
> shared_source = callbacks.cc callbacks.hh connection.cc connection.hh \
> marshall.cc marshall.hh rpc.hh status.hh
>
> @@ -344,7 +342,7 @@ libcc1_la_LINK = $(LIBTOOL) --tag=CXX $(AM_LIBTOOLFLAGS) \
> $(LIBTOOLFLAGS) --mode=link $(CXXLD) $(AM_CXXFLAGS) \
> $(CXXFLAGS) $(libcc1_la_LDFLAGS) $(LTLDFLAGS) -o $@
>
> -all: $(BUILT_SOURCES) cc1plugin-config.h
> +all: cc1plugin-config.h
> $(MAKE) $(AM_MAKEFLAGS) all-am
>
> .SUFFIXES:
> @@ -567,15 +565,13 @@ GTAGS:
> distclean-tags:
> -rm -f TAGS ID GTAGS GRTAGS GSYMS GPATH tags
> check-am: all-am
> -check: $(BUILT_SOURCES)
> - $(MAKE) $(AM_MAKEFLAGS) check-am
> +check: check-am
> all-am: Makefile $(LTLIBRARIES) cc1plugin-config.h
> installdirs:
> for dir in "$(DESTDIR)$(cc1libdir)" "$(DESTDIR)$(plugindir)"; do \
> test -z "$$dir" || $(MKDIR_P) "$$dir"; \
> done
> -install: $(BUILT_SOURCES)
> - $(MAKE) $(AM_MAKEFLAGS) install-am
> +install: install-am
> install-exec: install-exec-am
> install-data: install-data-am
> uninstall: uninstall-am
> @@ -595,7 +591,6 @@ install-strip:
> "INSTALL_PROGRAM_ENV=STRIPPROG='$(STRIP)'" install; \
> fi
> mostlyclean-generic:
> - -test -z "$(MOSTLYCLEANFILES)" || rm -f $(MOSTLYCLEANFILES)
>
> clean-generic:
>
> @@ -606,7 +601,6 @@ distclean-generic:
> maintainer-clean-generic:
> @echo "This command is intended for maintainers to use"
> @echo "it deletes files that may require special tools to rebuild."
> - -test -z "$(BUILT_SOURCES)" || rm -f $(BUILT_SOURCES)
> clean: clean-am
>
> clean-am: clean-cc1libLTLIBRARIES clean-generic clean-libtool \
> @@ -681,7 +675,7 @@ ps-am:
>
> uninstall-am: uninstall-cc1libLTLIBRARIES uninstall-pluginLTLIBRARIES
>
> -.MAKE: all check install install-am install-strip
> +.MAKE: all install-am install-strip
>
> .PHONY: CTAGS GTAGS all all-am am--refresh check check-am clean \
> clean-cc1libLTLIBRARIES clean-generic clean-libtool \
> @@ -702,21 +696,6 @@ uninstall-am: uninstall-cc1libLTLIBRARIES uninstall-pluginLTLIBRARIES
> override CXXFLAGS := $(filter-out -fsanitize=address,$(CXXFLAGS))
> override LDFLAGS := $(filter-out -fsanitize=address,$(LDFLAGS))
>
> -# Put this in a header so we don't run sed for each compilation. This
> -# is also simpler to debug as one can easily see the constant.
> -# FIXME: compute it in configure.ac and output it in config.status, or
> -# introduce timestamp files for some indirection to avoid rebuilding it
> -# every time.
> -c-compiler-name.h: Makefile
> - -rm -f $@T
> - echo "#define C_COMPILER_NAME \"`echo gcc | sed '$(transform)'`\"" > $@T
> - mv $@T $@ # $(SHELL) $(srcdir)/../move-if-change $@T $@
> -
> -cp-compiler-name.h: Makefile
> - -rm -f $@T
> - echo "#define CP_COMPILER_NAME \"`echo g++ | sed '$(transform)'`\"" > $@T
> - mv $@T $@ # $(SHELL) $(srcdir)/../move-if-change $@T $@
> -
> # Tell versions [3.59,3.63) of GNU make to not export all variables.
> # Otherwise a system limit (for SysV at least) may be exceeded.
> .NOEXPORT:
> diff --git a/libcc1/compiler-name.hh b/libcc1/compiler-name.hh
> new file mode 100644
> index 00000000000..30cdc41838b
> --- /dev/null
> +++ b/libcc1/compiler-name.hh
> @@ -0,0 +1,29 @@
> +/* The names of the compilers we use.
> + Copyright (C) 2017 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/>. */
> +
> +#ifndef COMPILER_NAME_H
> +#define COMPILER_NAME_H
> +
> +// C compiler name.
> +#define C_COMPILER_NAME "gcc"
> +
> +// C++ compiler name.
> +#define CP_COMPILER_NAME "g++"
> +
> +#endif // ! COMPILER_NAME_H
> diff --git a/libcc1/libcc1.cc b/libcc1/libcc1.cc
> index 0ef6c112dae..1a20dd941a4 100644
> --- a/libcc1/libcc1.cc
> +++ b/libcc1/libcc1.cc
> @@ -37,7 +37,7 @@ along with GCC; see the file COPYING3. If not see
> #include "libiberty.h"
> #include "xregex.h"
> #include "findcomp.hh"
> -#include "c-compiler-name.h"
> +#include "compiler-name.hh"
> #include "intl.h"
>
> struct libcc1;
> diff --git a/libcc1/libcp1.cc b/libcc1/libcp1.cc
> index bbd8488af93..b4f9710e0e2 100644
> --- a/libcc1/libcp1.cc
> +++ b/libcc1/libcp1.cc
> @@ -37,7 +37,7 @@ along with GCC; see the file COPYING3. If not see
> #include "libiberty.h"
> #include "xregex.h"
> #include "findcomp.hh"
> -#include "cp-compiler-name.h"
> +#include "compiler-name.hh"
> #include "intl.h"
>
> struct libcp1;
--
Sergio
GPG key ID: 237A 54B1 0287 28BF 00EF 31F4 D0EB 7628 65FC 5E36
Please send encrypted e-mail if possible
http://sergiodj.net/