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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.
rui314/mold#402

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

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

Initially written by Ian Lance Taylor iant@golang.org.

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 backtrace-supported.h.in 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 https://itanium-cxx-abi.github.io/cxx-abi/abi-eh.html This API is provided by GCC and clang.