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Patch from Rui Ueyama, who says:

libbacktrace occasionally fails to decompress compressed debug info
even though the sections contain valid zlib streams. The cause of the
issue is an off-by-one error.

If a zlib data block is a plain data (uncompressed data), the next two
bytes contain the size of the block. These two bytes value is byte-
aligned, so if we read-ahead more than 8 bits, we need to unread it.

So, the correct condition to determine whether or not we need to
unread a byte is bits >= 8 and not bits > 8. Due to this error,
if the last read bits happened to end at a byte boundary, the next
byte would be skipped. That caused the decompression failure.

This bug was originally reported against the mold linker.

	* elf.c (elf_zlib_inflate): Don't skip initial aligned byte in
	uncompressed block.

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A C library that may be linked into a C/C++ program to produce symbolic backtraces

Initially written by Ian Lance Taylor

This is version 1.0. It is likely that this will always be version 1.0.

The libbacktrace library may be linked into a program or library and used to produce symbolic backtraces. Sample uses would be to print a detailed backtrace when an error occurs or to gather detailed profiling information. In general the functions provided by this library are async-signal-safe, meaning that they may be safely called from a signal handler.

The libbacktrace library is provided under a BSD license. See the source files for the exact license text.

The public functions are declared and documented in the header file backtrace.h, which should be #include'd by a user of the library.

Building libbacktrace will generate a file backtrace-supported.h, which a user of the library may use to determine whether backtraces will work. See the source file for the macros that it defines.

As of October 2020, libbacktrace supports ELF, PE/COFF, Mach-O, and XCOFF executables with DWARF debugging information. In other words, it supports GNU/Linux, *BSD, macOS, Windows, and AIX. The library is written to make it straightforward to add support for other object file and debugging formats.

The library relies on the C++ unwind API defined at This API is provided by GCC and clang.