Question

I am trying to compile a C program that requires the use of several libraries. The problem is, the order the libraries are linked in causes the compilation to fail.

Is there anyway to get GCC to figure out the correct order, or for me to figure out the correct order without having to try every possibility?

mipsel-linux-gcc ffmpeg_mips_test.c -o ffmpeg_mips_test -Wall -v -I/ffmpegMIPS/includeffmpegMIPS/
                 -L/ffmpegMIPS/libffmpegMIPS/ -lavformat -lavcodec -lavutil -lswscale -lm -lpthread

The way I am doing it at the moment, is starting off with one, and then adding more libraries as the errors occur, however sometimes it feels like progress and then sometimes it just seems like I hit a dead end.

[edit]The compilation fails because of undefined references[/edit]

Answer 1

You have a few options

1) You can add additional calls to your library(s) that have dependencies

2) You can use the --start-group / --end-group options like so:

mipsel-linux-gcc ffmpeg_mips_test.c -o ffmpeg_mips_test -Wall -v -I/ffmpegMIPS/includeffmpegMIPS/
-L/ffmpegMIPS/libffmpegMIPS/ -Wl,--start-group -lavformat -lavcodec -lavutil -lswscale -Wl,--end-group -lm -lpthread

Here is the ld manpage entry describing its use

The specified archives are searched
repeatedly until no new undefined
references are created. Normally, an
archive is searched only once in the
order that it is specified on the
command line. If a symbol in that
archive is needed to resolve an
undefined symbol referred to by an
object in an archive that appears
later on the command line, the linker
would not be able to resolve that
reference. By grouping the archives,
they all be searched repeatedly until
all possible references are resolved.