MK27

So far, the only linker flags I've used have been as per some instructions...now, however, I'm trying to use libmpg123 (for which there are no online examples beyond their own API), and when I kept getting "undefined references" to functions that are exported by the included header (mpg123.h) I thought, why not try one of those -l thingies. So -lmpg123 got my test script past the compiler, but then when I run it:

./a.out: error while loading shared libraries: libmpg123.so.0: cannot open shared object file: No such file or directory

libmpg123.so.... is there, tho, so there must be some more different flags I need.
[edit: should have tried ldconfig!]

Given that I have the header and know where to find the libraries that I built from source, how can I determine (-lmpg123 was an easy guess) what flags I need to get everything to run?

Maybe there is some reading related to this somewhere?

__________________

Accuracy and integrity mean nothing if you don't make it past the censors...PYTHAGORAS

C_ntua

See this:
http://www.network-theory.co.uk/docs...cintro_17.html

MK27

This is useful to me, thanks...except it implies that there is no way to know except via educated guesses.

Anyone used _supported_decoders with mpg123 ? Or compiled anything with mpg123.h?

[later] so i forgot to call ldconfig after I "make install'd" mpg123 (isn't that usually done automatically?)
Anyway, for posterity, for at least some of the extended functions (the ones I tried so far), -lmpg123 is fine. But the proper flagset is in the examples makefile and it involves pkg-config:
gcc test.c `pkg-config --cflags --libs libmpg123`

__________________

Accuracy and integrity mean nothing if you don't make it past the censors...PYTHAGORAS

CornedBee

True. Well, you can also read the build system's source to find out the names it generates.

__________________
All the buzzt!
CornedBee

"There is not now, nor has there ever been, nor will there ever be, any programming language in which it is the least bit difficult to write bad code."
- Flon's Law

brewbuck

The link is happening fine. You are passing the right library name. The problem is that the linker search path is not the same as the loader search path, so ld.so is unable to find the library. You'll need to either move the library to some standard location or provide its explicit path in LD_LIBRARY_PATH

__________________
"Congratulations on your purchase. To begin using your quantum computer, set the power switch to both off and on simultaneously." -- raftpeople@slashdot

MK27

Yeah, exactly. Well, not exactly, because the library is in a standard path. But with my version of linux the loader uses a ld.so.cache file, which needs to be updated with ldconfig if you add new libraries into a standard path, or the loader won't find them (as if they weren't there).

__________________

Accuracy and integrity mean nothing if you don't make it past the censors...PYTHAGORAS