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[Craig Silverstein] PATCH: new format for compressed sections
- From: Ian Lance Taylor <iant at google dot com>
- To: binutils at sourceware dot org
- Date: Thu, 03 Apr 2008 07:17:24 -0700
- Subject: [Craig Silverstein] PATCH: new format for compressed sections
I committed this patch for Craig.
Date: Thu, 3 Apr 2008 00:19:15 -0700 (PDT)
From: csilvers@google.com (Craig Silverstein)
Lines: 206
Xref: localhost.localdomain mail.misc:169600
This patch goes along with the patch I've sent to the gdb folks, to
change the format of compressed debugging sections. I now store the
uncompressed length in the section proper, rather than in the section
name, so files will have dependable section names.
In the process of doing this, I noticed some brokenness in the
testsuite Makefiles for testing this feature.
craig
--cut here--
2008-04-03 Craig Silverstein <csilvers@google.com>
* compressed_output.h (class Output_compressed_section): Use
unsigned buffer.
* compressed_output.cc (zlib_compress): Use unsigned buffers,
add zlib header.
(zlib_compressed_suffix): Removed.
(Output_compressed_section::set_final_data_size): Use unsigned
buffers.
* testsuite/Makefile.am (flagstest_compress_debug_sections):
Fix linker invocation.
(flagstest_o_specialfile_and_compress_debug_sections):
Likewise.
* testsuite/Makefile.in: Regenerated.
Index: compressed_output.cc
===================================================================
RCS file: /cvs/src/src/gold/compressed_output.cc,v
retrieving revision 1.8
diff -p -u -r1.8 compressed_output.cc
--- compressed_output.cc 13 Mar 2008 21:04:21 -0000 1.8
+++ compressed_output.cc 3 Apr 2008 14:14:54 -0000
@@ -38,15 +38,21 @@ namespace gold
// (including not having zlib support in the library). If it returns
// true, it allocates memory for the compressed data using new, and
// sets *COMPRESSED_DATA and *COMPRESSED_SIZE to appropriate values.
+// It also writes a header before COMPRESSED_DATA: 4 bytes saying
+// "ZLIB", and 8 bytes indicating the uncompressed size, in big-endian
+// order.
#ifdef HAVE_ZLIB_H
static bool
-zlib_compress(const char* uncompressed_data, unsigned long uncompressed_size,
- char** compressed_data, unsigned long* compressed_size)
+zlib_compress(const unsigned char* uncompressed_data,
+ unsigned long uncompressed_size,
+ unsigned char** compressed_data,
+ unsigned long* compressed_size)
{
+ const int header_size = 12;
*compressed_size = uncompressed_size + uncompressed_size / 1000 + 128;
- *compressed_data = new char[*compressed_size];
+ *compressed_data = new unsigned char[*compressed_size + header_size];
int compress_level;
if (parameters->options().optimize() >= 1)
@@ -54,13 +60,19 @@ zlib_compress(const char* uncompressed_d
else
compress_level = 1;
- int rc = compress2(reinterpret_cast<Bytef*>(*compressed_data),
+ int rc = compress2(reinterpret_cast<Bytef*>(*compressed_data) + header_size,
compressed_size,
reinterpret_cast<const Bytef*>(uncompressed_data),
uncompressed_size,
compress_level);
if (rc == Z_OK)
- return true;
+ {
+ memcpy(*compressed_data, "ZLIB", 4);
+ elfcpp::Swap_unaligned<64, true>::writeval(*compressed_data + 4,
+ uncompressed_size);
+ *compressed_size += header_size;
+ return true;
+ }
else
{
delete[] *compressed_data;
@@ -72,24 +84,14 @@ zlib_compress(const char* uncompressed_d
#else // !defined(HAVE_ZLIB_H)
static bool
-zlib_compress(const char*, unsigned long, char**, unsigned long*)
+zlib_compress(const unsigned char*, unsigned long,
+ unsigned char**, unsigned long*)
{
return false;
}
#endif // !defined(HAVE_ZLIB_H)
-// After compressing an output section, we rename it from foo to
-// foo.zlib.nnnn, where nnnn is the uncompressed size of the section.
-
-static std::string
-zlib_compressed_suffix(unsigned long uncompressed_size)
-{
- char size_string[64];
- snprintf(size_string, sizeof(size_string), "%lu", uncompressed_size);
- return std::string(".zlib.") + size_string;
-}
-
// Class Output_compressed_section.
// Set the final data size of a compressed section. This is where
@@ -102,8 +104,7 @@ Output_compressed_section::set_final_dat
// (Try to) compress the data.
unsigned long compressed_size;
- unsigned char* u_uncompressed_data = this->postprocessing_buffer();
- char* uncompressed_data = reinterpret_cast<char*>(u_uncompressed_data);
+ unsigned char* uncompressed_data = this->postprocessing_buffer();
// At this point the contents of all regular input sections will
// have been copied into the postprocessing buffer, and relocations
@@ -117,8 +118,8 @@ Output_compressed_section::set_final_dat
&this->data_, &compressed_size);
if (success)
{
- std::string suffix(zlib_compressed_suffix(uncompressed_size));
- this->new_section_name_ = std::string(this->name()) + suffix;
+ // This converts .debug_foo to .zdebug_foo
+ this->new_section_name_ = std::string(".z") + (this->name() + 1);
this->set_name(this->new_section_name_.c_str());
this->set_data_size(compressed_size);
}
Index: compressed_output.h
===================================================================
RCS file: /cvs/src/src/gold/compressed_output.h,v
retrieving revision 1.3
diff -p -u -r1.3 compressed_output.h
--- compressed_output.h 13 Mar 2008 21:04:21 -0000 1.3
+++ compressed_output.h 3 Apr 2008 14:14:54 -0000
@@ -64,7 +64,7 @@ class Output_compressed_section : public
// The options--this includes the compression type.
const General_options* options_;
// The compressed data.
- char* data_;
+ unsigned char* data_;
// The new section name if we do compress.
std::string new_section_name_;
};
Index: testsuite/Makefile.am
===================================================================
RCS file: /cvs/src/src/gold/testsuite/Makefile.am,v
retrieving revision 1.53
diff -p -u -r1.53 Makefile.am
--- testsuite/Makefile.am 29 Mar 2008 08:39:26 -0000 1.53
+++ testsuite/Makefile.am 3 Apr 2008 14:14:54 -0000
@@ -507,7 +507,7 @@ undef_symbol.err: undef_symbol_main.o un
# Test --compress-debug-sections. FIXME: check we actually compress.
check_PROGRAMS += flagstest_compress_debug_sections
flagstest_compress_debug_sections: flagstest_debug.o gcctestdir/ld
- $(CXXLINK) -Bgcctestdir/ -o $@ $< --compress-debug-sections=zlib
+ $(CXXLINK) -Bgcctestdir/ -o $@ $< -Wl,--compress-debug-sections=zlib
test -s $@
@@ -523,7 +523,7 @@ flagstest_o_specialfile: flagstest_debug
check_PROGRAMS += flagstest_o_specialfile_and_compress_debug_sections
flagstest_o_specialfile_and_compress_debug_sections: flagstest_debug.o \
gcctestdir/ld
- $(CXXLINK) -Bgcctestdir/ -o /dev/stdout $< --compress-debug-sections=zlib 2>&1 | cat > $@
+ $(CXXLINK) -Bgcctestdir/ -o /dev/stdout $< -Wl,--compress-debug-sections=zlib 2>&1 | cat > $@
chmod a+x $@
test -s $@