CODEWITHSUNDEEP
gcclinkermakefileversioning
user626201
user626201

Reputation: 1682

Undefining linker symbols in gcc

We have a programm that runs on an embedded oOS. We normally embed a version string in the output binary that can identify all the versions contained when generating the binary. Usually the compilers we use can make sure that the version string is in the binary by creating an "undefined" symbol, which is then resolved by our version string.

However, we have now moved to a Linux based system and gcc.

gcc is removing the version string from the final exe. The final exe is created through linking in a bunch of libraries. Each library has a version string embedded.

gcc is removing the version string because nothing is referencing the string and we have turned on -Os optimisations.

Is there a way of making sure that gcc does not strip a collection of strings (there are about 5-10 version strings we need to embed)?

Thanks.

Upvotes: 0

Views: 2653

Answers (2)

user626201
user626201

Reputation: 1682

Ok, to solve this we did this in a c file:

const char _string_[] = "some string";

Then include the object file in the final link:

gcc <snip> -Wl,--start-group string.o <snip> -Wl,--end-group -Wl,--strip-all -o final.exe

Upvotes: 2

sinelaw
sinelaw

Reputation: 16553

Try working with --retain-symbols-file (option to the linker)

From the ld mangpage:

--retain-symbols-file filename Retain only the symbols listed in the file filename, discarding all others. filename is simply a flat file, with one symbol name per line. This option is especially useful in environments (such as VxWorks) where a large global symbol table is accumulated gradually, to conserve run-time memory.

--retain-symbols-file does not discard undefined symbols, or symbols needed for relocations.

You may only specify --retain-symbols-file once in the command line. It overrides -s and -S.

EDIT I just noticed the last line of the docs quoted above. It will override the 'strip all' option, so I'm not sure this will help you...

Upvotes: 3

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