#85392 - xyierz - Mon May 29, 2006 8:32 pm
Last night I was struggling with a linker error while trying to compile a library for the DS:
I found the cause of the error this morning. When I was asking about it in IRC, I was told that someone had posted here asking about this error, but I haven't been able to find the post.
Anyway, the problem is that for some reason the linker is trying to link signalr.o which does indeed contain an undefined reference to _kill. If you take a look at the symbols exported by signalr.o:
You'll notice that signalr.o exports the functions _getpid_r and _kill_r. Taking a look at which libc functions refer to these symbols:
Since mktemp.o, signal.o, and tmpnam.o all reference symbols defined in signalr.o, using any functions that they define will link in signalr.o and trigger the linker error. Using another objdump, I determined that the functions that these object files export are
mktemp.o: mktemp(), mkstemp()
signal.o: raise(), signal()
tmpnam.o: tempnam(), tmpnam()
For a proof of concept, I wrote a simple program with examples of all the function calls that trigger this error:
Since none of these functions are really very useful on the DS, probably the best fix is to simply avoid using them.
| Code: |
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/usr/local/devkitpro/devkitARM/bin/../lib/gcc/arm-elf/4.1.0/../../../../arm-elf/lib/interwork/libc.a(signalr.o): In function `_kill_r': : undefined reference to `_kill' |
I found the cause of the error this morning. When I was asking about it in IRC, I was told that someone had posted here asking about this error, but I haven't been able to find the post.
Anyway, the problem is that for some reason the linker is trying to link signalr.o which does indeed contain an undefined reference to _kill. If you take a look at the symbols exported by signalr.o:
| Code: |
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$ arm-elf-objdump -t libc.a signalr.o: file format elf32-littlearm SYMBOL TABLE: 00000000 l d .text 00000000 .text 00000000 l d .data 00000000 .data 00000000 l d .bss 00000000 .bss 00000000 l d .comment 00000000 .comment 00000000 g F .text 00000004 _getpid_r 00000000 *UND* 00000000 _getpid 00000004 g F .text 0000003c _kill_r 00000000 *UND* 00000000 _kill 00000000 *UND* 00000000 errno |
You'll notice that signalr.o exports the functions _getpid_r and _kill_r. Taking a look at which libc functions refer to these symbols:
| Code: |
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$ find . -name '*.a' | xargs arm-elf-nm -u -A | grep _getpid_r ./libc.a:mktemp.o: U _getpid_r ./libc.a:signal.o: U _getpid_r ./libc.a:tmpnam.o: U _getpid_r $ find . -name '*.a' | xargs arm-elf-nm -u -A | grep _kill_r ./libc.a:signal.o: U _kill_r |
Since mktemp.o, signal.o, and tmpnam.o all reference symbols defined in signalr.o, using any functions that they define will link in signalr.o and trigger the linker error. Using another objdump, I determined that the functions that these object files export are
mktemp.o: mktemp(), mkstemp()
signal.o: raise(), signal()
tmpnam.o: tempnam(), tmpnam()
For a proof of concept, I wrote a simple program with examples of all the function calls that trigger this error:
| Code: |
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#include <stdio.h> #include <stdlib.h> int main() { // the following libc function calls trigger the linker error signal(0, NULL); tmpnam(NULL); tempnam(NULL, NULL); mktemp(NULL); mkstemp(NULL); return 0; } |
Since none of these functions are really very useful on the DS, probably the best fix is to simply avoid using them.