gcc - errors compiling example xscreensaver

Question

I'm trying to compile the example screensaver simplesquares.c (from here). I have vroot.h, and this is the command I'm using:

gcc -lX11 -o simplesquares simplesquares.c

These are the errors returned:

/tmp/cc0FvxcU.o: In function `VirtualRootWindowOfScreen':
simplesquares.c:(.text+0x55): undefined reference to `XInternAtom'
simplesquares.c:(.text+0x82): undefined reference to `XQueryTree'
simplesquares.c:(.text+0x108): undefined reference to `XGetWindowProperty'
simplesquares.c:(.text+0x14c): undefined reference to `XFree'
/tmp/cc0FvxcU.o: In function `main':
simplesquares.c:(.text+0x17b): undefined reference to `XOpenDisplay'
simplesquares.c:(.text+0x1c8): undefined reference to `XCreateGC'
simplesquares.c:(.text+0x201): undefined reference to `XSetForeground'
simplesquares.c:(.text+0x295): undefined reference to `XFillRectangle'
simplesquares.c:(.text+0x2e3): undefined reference to `XClearWindow'
simplesquares.c:(.text+0x2ef): undefined reference to `XFlush'
collect2: error: ld returned 1 exit status

What is happening here, and how can I fix it?

linker errors... you need to include some library with -L/path/To/Lib -l libname — Grady Player, Mar 20 '14 at 02:26
http://stackoverflow.com/questions/1983465/what-do-i-need-to-do-to-link-with-xlib — 001, Mar 20 '14 at 02:30

score 3 · Accepted Answer · answered Mar 20 '14 at 02:27

3

Statically linked libraries should be at the end of the command line.

gcc -o simplesquares simplesquares.c -lX11

From http://gcc.gnu.org/onlinedocs/gcc/Link-Options.html:

It makes a difference where in the command you write this option; the linker searches and processes libraries and object files in the order they are specified. Thus, ‘foo.o -lz bar.o’ searches library ‘z’ after file foo.o but before bar.o. If bar.o refers to functions in ‘z’, those functions may not be loaded.

answered Mar 20 '14 at 02:27

shanet

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@GradyPlayer I just tried compiling with the `-lX11` in both places and got the same error with it at the front and no errors with it at the end. – shanet Mar 20 '14 at 02:28
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well then I stand corrected... well... maybe, I am not going to actually try myself ;) – Grady Player Mar 20 '14 at 02:29
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@GradyPlayer Found the documentation. See my updated answer if you're curious. :) – shanet Mar 20 '14 at 02:31
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ok I believe that, makes more sense than the have to be at the end. – Grady Player Mar 20 '14 at 03:24

gcc - errors compiling example xscreensaver

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