[RFC 2/2] Unwind: demangle symbol names

[Masatake YAMATO]

This patch is for demangling c++ symbols appeared in strack traces
with using cplus_demangle in GNU libiberty library,

I'm not sure this is acceptable or not because this change introdues a depedency
to a GPLv3+ library to strace.

This is an example of output of demangled stack trace:

fstat(5, {st_mode=S_IFREG|0664, st_size=0, ...}) = 0
 > /usr/lib64/libc-2.25.so(__fxstat64+0x12) [0xffd62]
 > /usr/lib64/libc-2.25.so(_IO_file_doallocate+0x5f) [0x717ff]
 > /usr/lib64/libc-2.25.so(_IO_doallocbuf+0x79) [0x81699]
 > /usr/lib64/libc-2.25.so(_IO_file_overflow+0x198) [0x807b8]
 > /usr/lib64/libc-2.25.so(_IO_file_xsputn+0xbd) [0x7ed5d]
 > /usr/lib64/libc-2.25.so(fwrite_unlocked+0x60) [0x7d800]
 > /usr/lib64/libleveldb.so.1.18(leveldb::EnvWrapper::StartThread+0x3b6) [0x48656]
 > /usr/lib64/libleveldb.so.1.18(leveldb::log::Writer::EmitPhysicalRecord+0x89) [0x28bc9]
 > /usr/lib64/libleveldb.so.1.18(leveldb::log::Writer::AddRecord+0x9e) [0x28d9e]
 > /usr/lib64/libleveldb.so.1.18(leveldb::DBImpl::Write+0x208) [0x1ce18]
 > /usr/lib64/libleveldb.so.1.18(leveldb::DB::Put+0x59) [0x192b9]
 > /usr/lib64/libleveldb.so.1.18(leveldb::DBImpl::Put+0x1d) [0x1931d]
 > /home/yamato/var/leveldb/doc/a.out(main+0x120) [0x1107]
 > /usr/lib64/libc-2.25.so(__libc_start_main+0xea) [0x2088a]
 > /home/yamato/var/leveldb/doc/a.out(_start+0x2a) [0xf3a]
---
 Makefile.am  |  2 +-
 configure.ac | 10 ++++++++++
 unwind.c     | 18 ++++++++++++++++++
 3 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/Makefile.am b/Makefile.am
index 60376056..e69bd1fd 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -332,7 +332,7 @@ if USE_LIBUNWIND
 strace_SOURCES += unwind.c
 strace_CPPFLAGS += $(libunwind_CPPFLAGS)
 strace_LDFLAGS += $(libunwind_LDFLAGS)
-strace_LDADD += $(libunwind_LIBS)
+strace_LDADD += $(libunwind_LIBS) $(libiberty_LIBS)
 endif
 
 @CODE_COVERAGE_RULES@
diff --git a/configure.ac b/configure.ac
index fa451d84..b7ec9240 100644
--- a/configure.ac
+++ b/configure.ac
@@ -877,6 +877,16 @@ fi
 AM_CONDITIONAL([USE_LIBUNWIND], [test "x$use_libunwind" = xyes])
 AC_MSG_RESULT([$use_libunwind])
 
+libiberty_LIBS=
+if test "x$use_libunwind" = xyes; then
+   AC_CHECK_HEADERS([demangle.h],
+     [AC_CHECK_LIB([iberty], [cplus_demangle],
+       [libiberty_LIBS=-liberty
+        AC_DEFINE([USE_DEMANGLE], 1, [Do demangling symbols when tracking stack])
+       ])])
+  AC_SUBST(libiberty_LIBS)
+fi
+
 if test "$arch" = mips && test "$no_create" != yes; then
 	mkdir -p linux/mips
 	if $srcdir/linux/mips/genstub.sh linux/mips; then
diff --git a/unwind.c b/unwind.c
index 031795cc..bb357317 100644
--- a/unwind.c
+++ b/unwind.c
@@ -29,6 +29,10 @@
 #include <limits.h>
 #include <libunwind-ptrace.h>
 
+#ifdef USE_DEMANGLE
+#include <demangle.h>
+#endif
+
 #ifdef _LARGEFILE64_SOURCE
 # ifdef HAVE_FOPEN64
 #  define fopen_for_input fopen64
@@ -325,11 +329,25 @@ print_stack_frame(struct tcb *tcp,
 					&function_offset);
 			true_offset = ip - cur_mmap_cache->start_addr +
 				cur_mmap_cache->mmap_offset;
+
+#ifdef USE_DEMANGLE
+			char *demangled_name = cplus_demangle (*symbol_name, 0);
+#endif
+
 			call_action(data,
 				    cur_mmap_cache->binary_filename,
+#ifdef USE_DEMANGLE
+				    demangled_name? demangled_name: *symbol_name,
+#else
 				    *symbol_name,
+#endif
 				    function_offset,
 				    true_offset);
+#ifdef USE_DEMANGLE
+			if (demangled_name)
+				free (demangled_name);
+#endif
+
 			return 0;
 		} else if (ip < cur_mmap_cache->start_addr)
 			upper = mid - 1;
-- 
2.13.6