gcc generates shared object with execute permissions

Question

I am building a shared library on linux using gcc. I get no compile or link errors but my shared object always has the execution bit set (though readelf indicates its a shared object). I am just doing this:

> echo "int f() {return 1;}" > a.cpp
> gcc -c a.cpp
> gcc -shared -o liba.so a.o
> ls -l liba.so
-rwxr-xr-x 1 me me 6652 2011-06-09 17:05 liba.so

Why would a shared object have the execute bit set?

this is not gcc, this is your linker (`ld` or similar) – unbeli Jun 09 '11 at 21:20 — unbeli, Jun 09 '11 at 21:20

score 5 · Answer 1 · answered Jun 09 '11 at 21:39

5

Because generally you can execute shared libraries. Most shared libraries will crash when you execute them, but you can execute them.

Some libraries have an entry point defined (-Wl,-e,the_name_of_your_entry_point, the main function in standard C programs) defined, then you can execute them without a crash.

answered Jun 09 '11 at 21:39

ckruse

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You learn something everyday. Thanks, I'll file this away. Maybe it will be useful some day. – samwise Jun 09 '11 at 21:49

score 1 · Answer 2 · answered May 08 '12 at 16:16

HP-UX requires that shared libraries be executable, for example. If they're not, the memory map by the dynamic loader fails with permission denied. And presumably it doesn't hurt to have an x bit on other platforms, so GCC takes the safe route and sets the x bit.

gcc generates shared object with execute permissions

2 Answers2