CODEWITHSUNDEEP
ccross-compilinglibc
StoneThrow
StoneThrow

Reputation: 6295

How to check libc version?

This question is related to Why does pclose return prematurely?. I'd like to find out what version of libc is used for a cross-compiled executable. There are limitations, described below, that make the answers at Check glibc version for a particular gcc compiler not apply.

$ /path/to/toolchains/ARM-cortex-m3-4.4/bin/arm-uclinuxeabi-gcc -print-file-name=libc.so
libc.so
$
$ /path/to/toolchains/ARM-cortex-m3-4.4/bin/arm-uclinuxeabi-gcc -print-file-name=foo.bar
foo.bar
$ # I really do not have a foo.bar file in existence

$ ldd
sh: can't execute 'ldd': No such file or directory

My cross-toolchain seems to only provide libc.a, not libc.so.
I tried running that libc.a through /path/to/toolchains/ARM-cortex-m3-4.4/bin/arm-uclinuxeabi-nm and strings grepping (case-insensitive) for "version" and "libc" but did not find anything that looked like an identifying version.

The last thing I tried was strings /path/to/toolchains/ARM-cortex-m3-4.4/bin/arm-uclinuxeabi-gcc | grep GLIBC, which gave me:

GLIBC_2.3
GLIBC_2.2
GLIBC_2.1
GLIBC_2.0
EGLIBC configuration specifier, serves multilib purposes.

But that solution wasn't highly upvoted, and it also has a comment suggesting that it doesn't really give you the version. I don't really understand this answer or its responding comment, so I don't know what to make of its validity.

Question: given all the above, is there any definitive way to determine the libc version used for cross-compiling for this cross-platform?

Upvotes: 6

Views: 24492

Answers (1)

Nick ODell
Nick ODell

Reputation: 25444

You might be dealing with a variant of libc other than glibc. There are multiple different implementations of libc, such as musl or uclibc.

Here's a Bash script which can detect whether your compiler is using glibc or uclibc, and tells you the version if it detects either.

GCC_FEATURES=$(gcc -dM -E - <<< "#include <features.h>")

if grep -q __UCLIBC__ <<< "${GCC_FEATURES}"; then
    echo "uClibc"
    grep "#define __UCLIBC_MAJOR__" <<< "${GCC_FEATURES}"
    grep "#define __UCLIBC_MINOR__" <<< "${GCC_FEATURES}"
    grep "#define __UCLIBC_SUBLEVEL__" <<< "${GCC_FEATURES}"
elif grep -q __GLIBC__ <<< "${GCC_FEATURES}"; then
    echo "glibc"
    grep "#define __GLIBC__" <<< "${GCC_FEATURES}"
    grep "#define __GLIBC_MINOR__" <<< "${GCC_FEATURES}"
else
    echo "something else"
fi

(Source.)

If you're using musl, unfortunately this script will report "something else." There's no way to detect musl with a preprocessor macro, and this is intentional.

Upvotes: 9

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