Package: gcc-doc
Version: 5:4.9.2-1
Severity: normal
Hi. This relates to several details of linking, and I'm not sure if this
is a Debian or upstream bug.
The 'gcc' manpage says this:
-llibrary
...
The linker searches a standard list of directories for the
library, which is actually a file named liblibrary.a. The
linker then uses this file as if it had been specified
precisely by name.
...
Normally the files found this way are library files---archive
files whose members are object files. ...
This is not what actually happens. For instance, I have libarpack2-dev
installed. This ships both libarpack.a and libarpack.so. I build a
simple application like this:
$ gcc -o tst -larpack tst.c
Using strace to see what files are actually opened, I see this:
[pid 13833] open("/usr/lib/gcc/x86_64-linux-gnu/5/libarpack.so", O_RDONLY) = -1
ENOENT (No such file or directory)
[pid 13833] open("/usr/lib/gcc/x86_64-linux-gnu/5/libarpack.a", O_RDONLY) = -1
ENOENT (No such file or directory)
[pid 13833]
open("/usr/lib/gcc/x86_64-linux-gnu/5/../../../x86_64-linux-gnu/libarpack.so",
O_RDONLY) = -1 ENOENT (No such file or directory)
[pid 13833]
open("/usr/lib/gcc/x86_64-linux-gnu/5/../../../x86_64-linux-gnu/libarpack.a",
O_RDONLY) = -1 ENOENT (No such file or directory)
[pid 13833]
open("/usr/lib/gcc/x86_64-linux-gnu/5/../../../../lib/libarpack.so", O_RDONLY)
= 9
[pid 13833]
open("/usr/lib/gcc/x86_64-linux-gnu/5/../../../../lib/libarpack.so", O_RDONLY)
= 10
So in each path in the list we look for the .so and then the .a. The
manpage however implies that we only look for the .a, and while we DO
look for it, this isn't the first choice.
