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Re: A plan to get rid of unnecessary package dependencies

On Mon, Sep 25, 2006 at 02:40:49PM -0700, Kevin B. McCarty wrote:
> One thing I noticed is that there are a lot of "problems" (in your
> terminology) caused by unneeded dependencies on libgcc1
> (/lib/libgcc_s.so.1).  From my quick investigation, it appears that the
> C++ and Fortran compilers (g++, g77, gfortran) introduce this dependency
> automatically to programs linked with them.  However, if gcc is instead
> used in the linking step, no such dependency is created (at least on
> amd64 where I'm testing).
> That is, programs compiled like this have libgcc_s.so.1 NEEDED:
> g++ foo.cc
> g77 foo.F
> gfortran foo.F
> but if they are compiled to object code and then linked with plain
> vanilla gcc, like this, they don't:
> g++ -c foo.cc -o foo.o && gcc foo.o -lstdc++
> g77 -c foo.F -o foo.o && gcc foo.o -lg2c -lfrtbegin
> gfortran -c foo.F -o foo.o && gcc foo.o -lgfortran -lgfortranbegin
> [CC'ed to debian-gcc to see if someone there can explain why this happens.]

Atleast for g++, it ends up being linked to both -lm and -lgcc_s

Using g++ I get:
[pid 22315] execve("/usr/bin/ld", ["/usr/bin/ld", "--eh-frame-hdr", "-m", "elf_x86_64", "-dynamic-linker", "/lib64/ld-linux-x86-64.so.2", "-o", "foo", "/usr/lib/gcc/x86_64-linux-gnu/4.1.2/../../../../lib64/crt1.o", "/usr/lib/gcc/x86_64-linux-gnu/4.1.2/../../../../lib64/crti.o", "/usr/lib/gcc/x86_64-linux-gnu/4.1.2/crtbegin.o", "-L/usr/lib/gcc/x86_64-linux-gnu/4.1.2", "-L/usr/lib/gcc/x86_64-linux-gnu/4.1.2", "-L/usr/lib/gcc/x86_64-linux-gnu/4.1.2/../../../../lib64", "-L/lib/../lib64", "-L/usr/lib/../lib64", "foo.o", "-lstdc++", "-lm", "-lgcc_s", "-lgcc",
"-lc", "-lgcc_s", "-lgcc", "/usr/lib/gcc/x86_64-linux-gnu/4.1.2/crtend.o", "/usr/lib/gcc/x86_64-linux-gnu/4.1.2/../../../../lib64/crtn.o"], [/* 18 vars */]) = 0

Using gcc I get:
[pid 22347] execve("/usr/bin/ld", ["/usr/bin/ld", "--eh-frame-hdr", "-m", "elf_x86_64", "-dynamic-linker", "/lib64/ld-linux-x86-64.so.2", "-o", "foo", "/usr/lib/gcc/x86_64-linux-gnu/4.1.2/../../../../lib64/crt1.o", "/usr/lib/gcc/x86_64-linux-gnu/4.1.2/../../../../lib64/crti.o", "/usr/lib/gcc/x86_64-linux-gnu/4.1.2/crtbegin.o", "-L/usr/lib/gcc/x86_64-linux-gnu/4.1.2", "-L/usr/lib/gcc/x86_64-linux-gnu/4.1.2", "-L/usr/lib/gcc/x86_64-linux-gnu/4.1.2/../../../../lib64", "-L/lib/../lib64", "-L/usr/lib/../lib64", "foo.o", "-lstdc++", "-lgcc", "--as-needed", "-lgcc_s", "--no-as-needed", "-lc", "-lgcc", "--as-needed", "-lgcc_s", "--no-as-needed", "/usr/lib/gcc/x86_64-linux-gnu/4.1.2/crtend.o", "/usr/lib/gcc/x86_64-linux-gnu/4.1.2/../../../../lib64/crtn.o"], [/* 18 vars */]) = 0

Notice the --as-needed and --no-as-needed around the -lgcc_s's.

>From the specs:
%{static|static-libgcc:-lgcc -lgcc_eh}%{!static:%{!static-libgcc:%{!shared-libgcc:-lgcc --as-needed -lgcc_s --no-as-needed}%{shared-libgcc:-lgcc_s%{!shared: -lgcc}}}}

g++ seem to be using some other specs, but I have no idea how I
should dump them.


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