xz.git - XZ Utils

Age	Commit message (Collapse)	Author	Files	Lines
2023-03-07	liblzma: Avoid null pointer + 0 (undefined behavior in C).	Lasse Collin	1	-3/+10
	In the C99 and C17 standards, section 6.5.6 paragraph 8 means that adding 0 to a null pointer is undefined behavior. As of writing, "clang -fsanitize=undefined" (Clang 15) diagnoses this. However, I'm not aware of any compiler that would take advantage of this when optimizing (Clang 15 included). It's good to avoid this anyway since compilers might some day infer that pointer arithmetic implies that the pointer is not NULL. That is, the following foo() would then unconditionally return 0, even for foo(NULL, 0): void bar(char a, char b); int foo(char *a, size_t n) { bar(a, a + n); return a == NULL; } In contrast to C, C++ explicitly allows null pointer + 0. So if the above is compiled as C++ then there is no undefined behavior in the foo(NULL, 0) call. To me it seems that changing the C standard would be the sane thing to do (just add one sentence) as it would ensure that a huge amount of old code won't break in the future. Based on web searches it seems that a large number of codebases (where null pointer + 0 occurs) are being fixed instead to be future-proof in case compilers will some day optimize based on it (like making the above foo(NULL, 0) return 0) which in the worst case will cause security bugs. Some projects don't plan to change it. For example, gnulib and thus many GNU tools currently require that null pointer + 0 is defined: https://lists.gnu.org/archive/html/bug-gnulib/2021-11/msg00000.html https://www.gnu.org/software/gnulib/manual/html_node/Other-portability-assumptions.html In XZ Utils null pointer + 0 issue should be fixed after this commit. This adds a few if-statements and thus branches to avoid null pointer + 0. These check for size > 0 instead of ptr != NULL because this way bugs where size > 0 && ptr == NULL will likely get caught quickly. None of them are in hot spots so it shouldn't matter for performance. A little less readable version would be replacing ptr + offset with offset != 0 ? ptr + offset : ptr or creating a macro for it: #define my_ptr_add(ptr, offset) \ ((offset) != 0 ? ((ptr) + (offset)) : (ptr)) Checking for offset != 0 instead of ptr != NULL allows GCC >= 8.1, Clang >= 7, and Clang-based ICX to optimize it to the very same code as ptr + offset. That is, it won't create a branch. So for hot code this could be a good solution to avoid null pointer + 0. Unfortunately other compilers like ICC 2021 or MSVC 19.33 (VS2022) will create a branch from my_ptr_add(). Thanks to Marcin Kowalczyk for reporting the problem: https://github.com/tukaani-project/xz/issues/36
2023-01-09	liblzma: Add NULL check to lzma_index_hash_append.	Jia Tan	1	-1/+1
	This is for consistency with lzma_index_append.
2023-01-09	liblzma: Replaced hardcoded 0x0 index indicator byte with macro	Jia Tan	1	-1/+1

2022-03-06	liblzma: Index hash: Change return value type of hash_append() to void.	Lasse Collin	1	-6/+5

2018-10-26	liblzma: Don't verify header CRC32s if building for fuzz testing.	Lasse Collin	1	-1/+4
	FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION is #defined when liblzma is being built for fuzz testing. Most fuzzed inputs would normally get rejected because of incorrect CRC32 and the actual header decoding code wouldn't get fuzzed. Disabling CRC32 checks avoids this problem. The fuzzer program must still use LZMA_IGNORE_CHECK flag to disable verification of integrity checks of uncompressed data.
2012-07-17	liblzma: Make the use of lzma_allocator const-correct.	Lasse Collin	1	-2/+4
	There is a tiny risk of causing breakage: If an application assigns lzma_stream.allocator to a non-const pointer, such code won't compile anymore. I don't know why anyone would do such a thing though, so in practice this shouldn't cause trouble. Thanks to Jan Kratochvil for the patch.
2009-04-13	Put the interesting parts of XZ Utils into the public domain.	Lasse Collin	1	-10/+3
	Some minor documentation cleanups were made at the same time.
2009-02-02	Modify LZMA_API macro so that it works on Windows with	Lasse Collin	1	-5/+5
	other compilers than MinGW. This may hurt readability of the API headers slightly, but I don't know any better way to do this.
2008-11-19	Oh well, big messy commit again. Some highlights:	Lasse Collin	1	-34/+34
	- Updated to the latest, probably final file format version. - Command line tool reworked to not use threads anymore. Threading will probably go into liblzma anyway. - Memory usage limit is now about 30 % for uncompression and about 90 % for compression. - Progress indicator with --verbose - Simplified --help and full --long-help - Upgraded to the last LGPLv2.1+ getopt_long from gnulib. - Some bug fixes
2008-09-13	Renamed constants:	Lasse Collin	1	-7/+6
	- LZMA_VLI_VALUE_MAX -> LZMA_VLI_MAX - LZMA_VLI_VALUE_UNKNOWN -> LZMA_VLI_UNKNOWN - LZMA_HEADER_ERRRO -> LZMA_OPTIONS_ERROR
2008-08-28	Sort of garbage collection commit. :-\| Many things are still	Lasse Collin	1	-4/+4
	broken. API has changed a lot and it will still change a little more here and there. The command line tool doesn't have all the required changes to reflect the API changes, so it's easy to get "internal error" or trigger assertions.
2008-06-18	Update the code to mostly match the new simpler file format	Lasse Collin	1	-0/+340
	specification. Simplify things by removing most of the support for known uncompressed size in most places. There are some miscellaneous changes here and there too. The API of liblzma has got many changes and still some more will be done soon. While most of the code has been updated, some things are not fixed (the command line tool will choke with invalid filter chain, if nothing else). Subblock filter is somewhat broken for now. It will be updated once the encoded format of the Subblock filter has been decided.