Re: Questions related to creation of libgcov.so

[Martin Liška <mliska at suse dot cz>]

On 08/03/2018 04:42 PM, Joseph Myers wrote:
> On Fri, 3 Aug 2018, Jakub Jelinek wrote:
> 
>>> 3) Should I come up with a symbol versioning of the libgcov API?
>>
>> Certainly.
> 
> Furthermore, make sure that the libgcov.a symbols remain hidden (via 
> building the static objects with $(vis_hide), since you're removing 
> ATTRIBUTE_HIDDEN).
> 

Hello.

I'm sending second version of the patch candidate. I was able to create
a mapfile and generate versioned symbols for libgcov.so file.

Unresolved issues:
1) I still see linking with static library:

$ find /home/marxin/bin/gcc -name libgcov*
/home/marxin/bin/gcc/lib64/libgcov.so.1
/home/marxin/bin/gcc/lib64/gcc/x86_64-pc-linux-gnu/9.0.0/libgcov.a
/home/marxin/bin/gcc/lib64/libgcov.so

$ export PATH=/home/marxin/bin/gcc/bin/:$PATH && export LD_LIBRARY_PATH=/home/marxin/bin/gcc/lib64/:$LD_LIBRARY_PATH
$ gcc main.c -fprofile-generate -Wl,--verbose | grep gcov
attempt to open /home/marxin/bin/gcc/lib64/gcc/x86_64-pc-linux-gnu/9.0.0/libgcov.so failed
attempt to open /home/marxin/bin/gcc/lib64/gcc/x86_64-pc-linux-gnu/9.0.0/libgcov.a succeeded
(/home/marxin/bin/gcc/lib64/gcc/x86_64-pc-linux-gnu/9.0.0/libgcov.a)_gcov_merge_add.o
(/home/marxin/bin/gcc/lib64/gcc/x86_64-pc-linux-gnu/9.0.0/libgcov.a)_gcov_merge_time_profile.o
(/home/marxin/bin/gcc/lib64/gcc/x86_64-pc-linux-gnu/9.0.0/libgcov.a)_gcov_indirect_call_profiler_v2.o
(/home/marxin/bin/gcc/lib64/gcc/x86_64-pc-linux-gnu/9.0.0/libgcov.a)_gcov_time_profiler.o
(/home/marxin/bin/gcc/lib64/gcc/x86_64-pc-linux-gnu/9.0.0/libgcov.a)_gcov.o

2) Do I understand that correctly that I need to build .o files twice: once with hidden visibility and second time
without for the shared library?

3) I added t-libgcov t-libgcov-gld t-libgcov-elf-ver into *-linux for now. Am I right that it should be added
basically to all places where e.g. 't-slibgcc-elf-ver' is?

Alexander: I added the -Wl,-z,now.

Thanks,
Martin

>From 66ee61145c0bd864bb5046b7ce17344cf3c705ea Mon Sep 17 00:00:00 2001
From: marxin <mliska@suse.cz>
Date: Fri, 3 Aug 2018 11:14:15 +0200
Subject: [PATCH] Add libgcov.so: work in progress.

---
 libgcc/Makefile.in          | 38 +++++++++++++++++++++++++-
 libgcc/config.host          |  4 +--
 libgcc/config/t-libgcov     | 50 ++++++++++++++++++++++++++++++++++
 libgcc/config/t-libgcov-gld |  5 ++++
 libgcc/libgcov-profiler.c   |  6 ++---
 libgcc/libgcov-std.ver.in   | 53 +++++++++++++++++++++++++++++++++++++
 libgcc/libgcov.h            | 31 +++++++++++-----------
 7 files changed, 165 insertions(+), 22 deletions(-)
 create mode 100644 libgcc/config/t-libgcov
 create mode 100644 libgcc/config/t-libgcov-gld
 create mode 100644 libgcc/libgcov-std.ver.in

diff --git a/libgcc/Makefile.in b/libgcc/Makefile.in
index 0c5b264f717..63d18bf861b 100644
--- a/libgcc/Makefile.in
+++ b/libgcc/Makefile.in
@@ -944,7 +944,7 @@ libgcc.a libgcov.a libunwind.a libgcc_eh.a:
 
 all: libgcc.a
 ifeq ($(enable_gcov),yes)
-all: libgcov.a
+all: libgcov.a libgcov$(SHLIB_EXT)
 endif
 
 ifneq ($(LIBUNWIND),)
@@ -1006,6 +1006,38 @@ libunwind$(SHLIB_EXT): $(libunwind-s-objects) $(extra-parts)
 		@shlib_base_name@,libunwind,$(subst \
 		@shlib_slibdir_qual@,$(MULTIOSSUBDIR),$(SHLIBUNWIND_LINK))))))
 
+# Map-file generation.
+libgcov.map.in: $(SHLIBGCOV_MAPFILES)
+	{ cat $(SHLIBGCOV_MAPFILES) \
+	    | sed -e '/^[ 	]*#/d' \
+		  -e 's/^%\(if\|else\|elif\|endif\|define\)/#\1/' \
+	    | $(gcc_compile_bare) -E -xassembler-with-cpp -; \
+	} > tmp-$@
+	mv tmp-$@ $@
+libgcov.map: $(SHLIBGCOV_MKMAP) libgcov.map.in $(libgcov-objects)
+	{ $(NM) $(SHLIBGCOV_NM_FLAGS) $(libgcov-objects); echo %%; \
+	  cat libgcov.map.in; \
+	} | $(AWK) -f $(SHLIBGCOV_MKMAP) $(SHLIBGCOV_MKMAP_OPTS) > tmp-$@
+	mv tmp-$@ $@
+libgcov$(SHLIB_EXT): libgcov.map
+libgcov_mapfile = libgcov.map
+
+libgcov-std.ver: $(srcdir)/libgcov-std.ver.in
+	cat < $< > $@
+
+libgcov$(SHLIB_EXT): $(libgcov-objects) libgcc_s$(SHLIB_EXT)
+	# @multilib_flags@ is still needed because this may use
+	# $(GCC_FOR_TARGET) and $(LIBGCC2_CFLAGS) directly.
+	# @multilib_dir@ is not really necessary, but sometimes it has
+	# more uses than just a directory name.
+	$(mkinstalldirs) $(MULTIDIR)
+	$(subst @multilib_flags@,$(CFLAGS) -B./,$(subst \
+		@multilib_dir@,$(MULTIDIR),$(subst \
+		@shlib_objs@,$(objects),$(subst \
+		@shlib_base_name@,libgcov,$(subst \
+		@shlib_map_file@,$(libgcov_mapfile),$(subst \
+		@shlib_slibdir_qual@,$(MULTIOSSUBDIR),$(SHLIBGCOV_LINK)))))))
+
 endif
 
 # Build the standard GCC startfiles and endfiles.
@@ -1172,6 +1204,10 @@ ifeq ($(enable_gcov),yes)
 	$(INSTALL_DATA) libgcov.a $(DESTDIR)$(inst_libdir)/
 	chmod 644 $(DESTDIR)$(inst_libdir)/libgcov.a
 	$(RANLIB) $(DESTDIR)$(inst_libdir)/libgcov.a
+
+	$(subst @multilib_dir@,$(MULTIDIR),$(subst \
+		@shlib_base_name@,libgcov,$(subst \
+		@shlib_slibdir_qual@,$(MULTIOSSUBDIR),$(SHLIBGCOV_INSTALL))))
 endif
 
 	parts="$(INSTALL_PARTS)";				\
diff --git a/libgcc/config.host b/libgcc/config.host
index 18cabaf24f6..2d32046e27f 100644
--- a/libgcc/config.host
+++ b/libgcc/config.host
@@ -236,7 +236,7 @@ case ${host} in
   extra_parts="crtbegin.o crtend.o"
   ;;
 *-*-linux* | frv-*-*linux* | *-*-kfreebsd*-gnu | *-*-gnu* | *-*-kopensolaris*-gnu)
-  tmake_file="$tmake_file t-crtstuff-pic t-libgcc-pic t-eh-dw2-dip t-slibgcc t-slibgcc-gld t-slibgcc-elf-ver t-linux"
+  tmake_file="$tmake_file t-crtstuff-pic t-libgcc-pic t-eh-dw2-dip t-slibgcc t-slibgcc-gld t-slibgcc-elf-ver t-linux t-libgcov t-libgcov-gld t-libgcov-elf-ver"
   extra_parts="crtbegin.o crtbeginS.o crtbeginT.o crtend.o crtendS.o"
   if test x$enable_vtable_verify = xyes; then
     extra_parts="$extra_parts vtv_start.o vtv_end.o vtv_start_preinit.o vtv_end_preinit.o"
@@ -659,7 +659,7 @@ i[34567]86-*-kfreebsd*-gnu | i[34567]86-*-gnu* | i[34567]86-*-kopensolaris*-gnu)
 	;;
 x86_64-*-linux*)
 	extra_parts="$extra_parts crtprec32.o crtprec64.o crtprec80.o crtfastmath.o"
-	tmake_file="${tmake_file} i386/t-crtpc t-crtfm i386/t-crtstuff t-dfprules"
+	tmake_file="${tmake_file} i386/t-crtpc t-crtfm i386/t-crtstuff t-dfprulesi"
 	tm_file="${tm_file} i386/elf-lib.h"
 	md_unwind_header=i386/linux-unwind.h
 	;;
diff --git a/libgcc/config/t-libgcov b/libgcc/config/t-libgcov
new file mode 100644
index 00000000000..5595d37ed96
--- /dev/null
+++ b/libgcc/config/t-libgcov
@@ -0,0 +1,50 @@
+# Copyright (C) 2018 Free Software Foundation, Inc.
+#
+# This file is part of GCC.
+#
+# GCC is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3, or (at your option)
+# any later version.
+#
+# GCC is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with GCC; see the file COPYING3.  If not see
+# <http://www.gnu.org/licenses/>.
+
+# Build libgcov for ELF with the GNU linker.
+
+SHLIBGCOV_SOLINK = @shlib_base_name@.so
+SHLIBGCOV_OBJS = @shlib_objs@
+SHLIBGCOV_DIR = @multilib_dir@
+SHLIBGCOV_SLIBDIR_QUAL = @shlib_slibdir_qual@
+SHLIBGCOV_MAP = @shlib_map_file@
+
+SHLIBGCOV_SOVERSION = 1
+SHLIBGCOV_SONAME = @shlib_base_name@.so.$(SHLIBGCOV_SOVERSION)
+
+SHLIBGCOV_LINK = $(CC) $(LIBGCC2_CFLAGS) -shared \
+	$(SHLIBGCOV_LDFLAGS) \
+	-nodefaultlibs -Wl,-h,$(SHLIBGCOV_SONAME) \
+	-Wl,-z,text -Wl,-z,defs -Wl,-z,now -o $(SHLIBGCOV_DIR)/$(SHLIBGCOV_SONAME).tmp \
+	@multilib_flags@ $(SHLIBGCOV_OBJS) -lc -lgcc && \
+	rm -f $(SHLIBGCOV_DIR)/$(SHLIBGCOV_SOLINK) && \
+	if [ -f $(SHLIBGCOV_DIR)/$(SHLIBGCOV_SONAME) ]; then \
+	  mv -f $(SHLIBGCOV_DIR)/$(SHLIBGCOV_SONAME) \
+		$(SHLIBGCOV_DIR)/$(SHLIBGCOV_SONAME).backup; \
+	else true; fi && \
+	mv $(SHLIBGCOV_DIR)/$(SHLIBGCOV_SONAME).tmp \
+	   $(SHLIBGCOV_DIR)/$(SHLIBGCOV_SONAME) && \
+	$(LN_S) $(SHLIBGCOV_SONAME) $(SHLIBGCOV_DIR)/$(SHLIBGCOV_SOLINK)
+
+SHLIBGCOV_INSTALL = \
+	$(SHELL) $(srcdir)/mkinstalldirs $(DESTDIR)$(slibdir)$(SHLIBGCOV_SLIBDIR_QUAL); \
+	$(INSTALL_DATA) $(SHLIBGCOV_DIR)/$(SHLIBGCOV_SONAME) \
+	  $(DESTDIR)$(slibdir)$(SHLIBGCOV_SLIBDIR_QUAL)/$(SHLIBGCOV_SONAME); \
+	rm -f $(DESTDIR)$(slibdir)$(SHLIBGCOV_SLIBDIR_QUAL)/$(SHLIBGCOV_SOLINK); \
+	$(LN_S) $(SHLIBGCOV_SONAME) \
+	  $(DESTDIR)$(slibdir)$(SHLIBGCOV_SLIBDIR_QUAL)/$(SHLIBGCOV_SOLINK)
diff --git a/libgcc/config/t-libgcov-gld b/libgcc/config/t-libgcov-gld
new file mode 100644
index 00000000000..3a00239e22e
--- /dev/null
+++ b/libgcc/config/t-libgcov-gld
@@ -0,0 +1,5 @@
+# Build a shared libgcov library for ELF with symbol versioning
+# with the GNU linker.
+
+SHLIBGCOV_LDFLAGS = -Wl,--soname=$(SHLIBGCOV_SONAME) \
+	-Wl,--version-script=$(SHLIBGCOV_MAP)
diff --git a/libgcc/libgcov-profiler.c b/libgcc/libgcov-profiler.c
index 7e208d75d86..df20e73b4e1 100644
--- a/libgcc/libgcov-profiler.c
+++ b/libgcc/libgcov-profiler.c
@@ -271,12 +271,12 @@ __gcov_topn_value_profiler_body (gcov_type *counters, gcov_type value)
 #if defined(HAVE_CC_TLS) && !defined (USE_EMUTLS)
 __thread
 #endif
-gcov_type *__gcov_indirect_call_topn_counters ATTRIBUTE_HIDDEN;
+gcov_type *__gcov_indirect_call_topn_counters;
 
 #if defined(HAVE_CC_TLS) && !defined (USE_EMUTLS)
 __thread
 #endif
-void *__gcov_indirect_call_topn_callee ATTRIBUTE_HIDDEN;
+void *__gcov_indirect_call_topn_callee;
 
 #ifdef TARGET_VTABLE_USES_DESCRIPTORS
 #define VTABLE_USES_DESCRIPTORS 1
@@ -344,7 +344,7 @@ __gcov_indirect_call_profiler_v2 (gcov_type value, void* cur_func)
 #ifdef L_gcov_time_profiler
 
 /* Counter for first visit of each function.  */
-gcov_type __gcov_time_profiler_counter ATTRIBUTE_HIDDEN;
+gcov_type __gcov_time_profiler_counter;
 
 #endif
 
diff --git a/libgcc/libgcov-std.ver.in b/libgcc/libgcov-std.ver.in
new file mode 100644
index 00000000000..71fa43e26c9
--- /dev/null
+++ b/libgcc/libgcov-std.ver.in
@@ -0,0 +1,53 @@
+# Copyright (C) 2018 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/>.
+
+GCC_9.1.0 {
+  __gcov_init
+  __gcov_exit
+  __gcov_merge_add
+  __gcov_merge_time_profile
+  __gcov_merge_single
+  __gcov_merge_ior
+  __gcov_merge_icall_topn
+  __gcov_interval_profiler
+  __gcov_interval_profiler_atomic
+  __gcov_pow2_profiler
+  __gcov_pow2_profiler_atomic
+  __gcov_one_value_profiler
+  __gcov_one_value_profiler_atomic
+  __gcov_indirect_call_profiler_v2
+  __gcov_time_profiler
+  __gcov_time_profiler_atomic
+  __gcov_average_profiler
+  __gcov_average_profiler_atomic
+  __gcov_ior_profiler
+  __gcov_ior_profiler_atomic
+  __gcov_indirect_call_topn_profiler
+
+  __gcov_fork
+  __gcov_execl
+  __gcov_execlp
+  __gcov_execle
+  __gcov_execv
+  __gcov_execvp
+  __gcov_execve
+
+  __gcov_indirect_call_callee
+  __gcov_indirect_call_counters
+  __gcov_time_profiler_counter
+}
diff --git a/libgcc/libgcov.h b/libgcc/libgcov.h
index 21422873cf2..d47e3fec703 100644
--- a/libgcc/libgcov.h
+++ b/libgcc/libgcov.h
@@ -234,10 +234,10 @@ extern struct gcov_master __gcov_master;
 extern void __gcov_dump_one (struct gcov_root *) ATTRIBUTE_HIDDEN;
 
 /* Register a new object file module.  */
-extern void __gcov_init (struct gcov_info *) ATTRIBUTE_HIDDEN;
+extern void __gcov_init (struct gcov_info *);
 
 /* GCOV exit function registered via a static destructor.  */
-extern void __gcov_exit (void) ATTRIBUTE_HIDDEN;
+extern void __gcov_exit (void);
 
 /* Function to reset all counters to 0.  Both externally visible (and
    overridable) and internal version.  */
@@ -247,19 +247,19 @@ extern void __gcov_reset_int (void) ATTRIBUTE_HIDDEN;
 extern void __gcov_dump_int (void) ATTRIBUTE_HIDDEN;
 
 /* The merge function that just sums the counters.  */
-extern void __gcov_merge_add (gcov_type *, unsigned) ATTRIBUTE_HIDDEN;
+extern void __gcov_merge_add (gcov_type *, unsigned);
 
 /* The merge function to select the minimum valid counter value.  */
-extern void __gcov_merge_time_profile (gcov_type *, unsigned) ATTRIBUTE_HIDDEN;
+extern void __gcov_merge_time_profile (gcov_type *, unsigned);
 
 /* The merge function to choose the most common value.  */
-extern void __gcov_merge_single (gcov_type *, unsigned) ATTRIBUTE_HIDDEN;
+extern void __gcov_merge_single (gcov_type *, unsigned);
 
 /* The merge function that just ors the counters together.  */
-extern void __gcov_merge_ior (gcov_type *, unsigned) ATTRIBUTE_HIDDEN;
+extern void __gcov_merge_ior (gcov_type *, unsigned);
 
 /* The merge function is used for topn indirect call counters.  */
-extern void __gcov_merge_icall_topn (gcov_type *, unsigned) ATTRIBUTE_HIDDEN;
+extern void __gcov_merge_icall_topn (gcov_type *, unsigned);
 
 /* The profiler functions.  */
 extern void __gcov_interval_profiler (gcov_type *, gcov_type, int, unsigned);
@@ -277,18 +277,17 @@ extern void __gcov_average_profiler_atomic (gcov_type *, gcov_type);
 extern void __gcov_ior_profiler (gcov_type *, gcov_type);
 extern void __gcov_ior_profiler_atomic (gcov_type *, gcov_type);
 extern void __gcov_indirect_call_topn_profiler (gcov_type, void *);
-extern void gcov_sort_n_vals (gcov_type *, int);
+extern void gcov_sort_n_vals (gcov_type *, int) ATTRIBUTE_HIDDEN;
 
 #ifndef inhibit_libc
 /* The wrappers around some library functions..  */
-extern pid_t __gcov_fork (void) ATTRIBUTE_HIDDEN;
-extern int __gcov_execl (const char *, char *, ...) ATTRIBUTE_HIDDEN;
-extern int __gcov_execlp (const char *, char *, ...) ATTRIBUTE_HIDDEN;
-extern int __gcov_execle (const char *, char *, ...) ATTRIBUTE_HIDDEN;
-extern int __gcov_execv (const char *, char *const []) ATTRIBUTE_HIDDEN;
-extern int __gcov_execvp (const char *, char *const []) ATTRIBUTE_HIDDEN;
-extern int __gcov_execve (const char *, char  *const [], char *const [])
-  ATTRIBUTE_HIDDEN;
+extern pid_t __gcov_fork (void);
+extern int __gcov_execl (const char *, char *, ...);
+extern int __gcov_execlp (const char *, char *, ...);
+extern int __gcov_execle (const char *, char *, ...);
+extern int __gcov_execv (const char *, char *const []);
+extern int __gcov_execvp (const char *, char *const []);
+extern int __gcov_execve (const char *, char  *const [], char *const []);
 
 /* Functions that only available in libgcov.  */
 GCOV_LINKAGE int gcov_open (const char */*name*/) ATTRIBUTE_HIDDEN;
-- 
2.18.0