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David Haller <gentoo@×××××××.de> [16-10-02 06:16]: |
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> Hello, |
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> |
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> On Sun, 02 Oct 2016, Meino.Cramer@×××.de wrote: |
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> >Suppose I would compile a program, which uses shared libraries and I |
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> >specify an additional library, which will be completly unused by the |
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> >code...will the resulting executable differ from an executable which |
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> >is compiled without this library ? |
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> |
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> Suppose you'd just test it? |
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> |
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> $ echo 'int main(void) {return 0;}' > t.c |
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> $ gcc -o t_nolib t.c |
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> $ gcc -o t_lib -lglib t.c |
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> $ gcc -o t_lib_as -Wl,-as-needed -lglib t.c |
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> $ gcc -o t_lib_nas -Wl,-no-as-needed -lglib t.c |
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> $ cmp t_nolib t_lib_as; echo $? |
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> 0 |
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> |
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> |
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> $ ls -l |
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> -rw-r----- 1 dh dh 27 Oct 2 05:40 t.c |
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> -rwxr-x--- 1 dh dh 6824 Oct 2 05:40 t_lib |
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> -rwxr-x--- 1 dh dh 6424 Oct 2 05:40 t_lib_as |
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> -rwxr-x--- 1 dh dh 6824 Oct 2 05:40 t_lib_nas |
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> -rwxr-x--- 1 dh dh 6424 Oct 2 05:40 t_nolib |
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> |
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> $ ldd t_* |
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> t_lib: |
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> linux-vdso.so.1 (0x00007fff0b7ff000) |
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> libglib-1.2.so.0 => /usr/lib64/libglib-1.2.so.0 (0x00007f372b55b000) |
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> libc.so.6 => /lib64/libc.so.6 (0x00007f372b1bb000) |
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> libdl.so.2 => /lib64/libdl.so.2 (0x00007f372afb7000) |
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> /lib64/ld-linux-x86-64.so.2 (0x00007f372b793000) |
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> t_lib_as: |
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> linux-vdso.so.1 (0x00007fffadf70000) |
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> libc.so.6 => /lib64/libc.so.6 (0x00007ff9289d7000) |
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> /lib64/ld-linux-x86-64.so.2 (0x00007ff928d77000) |
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> t_lib_nas: |
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> linux-vdso.so.1 (0x00007fffe9e6f000) |
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> libglib-1.2.so.0 => /usr/lib64/libglib-1.2.so.0 (0x00007f2a43afb000) |
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> libc.so.6 => /lib64/libc.so.6 (0x00007f2a4375b000) |
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> libdl.so.2 => /lib64/libdl.so.2 (0x00007f2a43557000) |
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> /lib64/ld-linux-x86-64.so.2 (0x00007f2a43d33000) |
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> t_nolib: |
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> linux-vdso.so.1 (0x00007fffbed58000) |
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> libc.so.6 => /lib64/libc.so.6 (0x00007fe55b4f4000) |
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> /lib64/ld-linux-x86-64.so.2 (0x00007fe55b894000) |
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> |
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> So: YES, it will differ unless you use the "-as-needed" ld flag. Which |
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> is why some distros have -as-needed as a default linker flag, to prune |
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> deps of packages, even though it causes "trouble" at times ... |
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> |
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> -dnh |
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> |
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> -- |
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> Graphisch??? Wie meinen? Hast du zuviel Fleisch von zu "gluecklichen" |
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> Rindern gefuttert? *scnr* Wozu zum Henker sollte man sowas brauchen? |
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> Logo ginge auch per ASCII :) (Logo? welches Logo? Wozu ueberhaupt?) |
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> [David Haller in suse-linux] |
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> |
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|
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Hi David, Hi Michael, |
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|
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thanks a LOT for your heavy testing!!! |
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I didn't thought, that the answers are THAT various... |
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I only thought of one answer at all... X) |
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|
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One curious question remains: |
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If -as-needed is included, all libs will be "delinked" :), which |
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are not used...so I am throwing away stuff, which no code calls: |
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WHY should this cause trouble? |
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Or is it again oversimplified by me? :) ;) 8) |
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|
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Cheers, |
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Meino |
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