如何判断一个库是否是用 -g 编译的？

Question

I have some compiled libraries on x86 Linux and I want to quickly determine whether they were compiled with debugging symbols.

Answer 1

The suggested command

objdump --debugging libinspected.a
objdump --debugging libinspected.so

gives me always the same result at least on Ubuntu/Linaro 4.5.2:

libinspected.a:     file format elf64-x86-64
libinspected.so:     file format elf64-x86-64

no matter whether the archive/shared library was built with or without -g option

What really helped me to determine whether -g was used is readelf tool:

readelf --debug-dump=decodedline libinspected.so

or

readelf --debug-dump=line libinspected.so

This will print out set of lines consisting of source filename, line number and address if such debug info is included into library , otherwise it'll print nothing .

You may pass whatever value you'll find necessary for --debug-dump option instead of decodedline .

Answer 2

If you're running on Linux, use objdump --debugging . There should be an entry for each object file in the library. For object files without debugging symbols, you'll see something like:

objdump --debugging libvoidincr.a
In archive libvoidincr.a:

voidincr.o:     file format elf64-x86-64

If there are debugging symbols, the output will be much more verbose.

Answer 3

nm -a <lib> will print all symbols from library, including debug ones.

So you can compare the outputs of nm <lib> and nm -a <lib> - if they differ, your lib contains some debug symbols.

Answer 4

What helped is:

gdb mylib.so

It prints when debug symbols are not found:

Reading symbols from mylib.so...(no debugging symbols found)...done.

Or when found:

Reading symbols from mylib.so...done.

None of earlier answers were giving meaningful results for me: libs without debug symbols were giving lots of output, etc.

Answer 5

On OSX you can use dsymutil -s and dwarfdump .

Using dsymutil -s <lib_file> | more dsymutil -s <lib_file> | more you will see source file paths in files that have debug symbols, but only the function names otherwise.

Answer 6

You can use objdump for this.

EDIT: From the man-page:

-W
--dwarf
Displays  the  contents of the DWARF debug sections in the file, if
any are present.

Answer 7

Answers suggesting the use of objdump --debugging or readelf --debug-dump=... don't work in the case that debug information is stored in a file separate from the binary, ie the binary contains a debug link section. Perhaps one could call that a bug in readelf .

The following code should handle this correctly:

# Test whether debug information is available for a given binary
has_debug_info() {
  readelf -S "$1" | grep -q " \(.debug_info\)\|\(.gnu_debuglink\) "
}

See Separate Debug Files in the GDB manual for more information.

Answer 8

https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/6/html/developer_guide/debugging

The command readelf -wi file is a good verification of debuginfo, compiled within your program.