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Any reason 

cc -g -lm -DBLITZ_HOST_IS_LITTLE_ENDIAN

would produce an error with code using math.h? Is it possible there's a difference between GCC version 4.0.3 (documented working version) and version 4.6.3 (my current version)?

makefile and asm.c @ https://gist.github.com/3801291

This is on ubuntu 12.04

My terminal output is a comment in the gist.

G. Sliepen
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BSull
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2 Answers2

12

Instead of 

cc -g -lm -DBLITZ_HOST_IS_LITTLE_ENDIAN foo.c

Try:

cc -g -DBLITZ_HOST_IS_LITTLE_ENDIAN foo.c -lm

When the linker searches a library, it links in modules that contain definitions for previously-undefined symbols.

If the linker searches -lm before foo.o, then pow() is not yet undefined. Conversely, if foo.o comes first, it undefines pow(), which -lm can then resolve.

EDIT: To accomplish this advice in your makefile, make these changes:

CFLAGS=-g -DBLITZ_HOST_IS_LITTLE_ENDIAN
LDLIBS=-lm

...

asm: asm.c
        $(CC) $(CFLAGS) asm.c $(LDLIBS) -o asm
Robᵩ
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  • Then tell us more about your compilation environment, the precise *entire* command line, and a sample program. – Robᵩ Sep 28 '12 at 17:56
  • I just noticed the makefile still puts -lm before asm.c so I'm going to try and go around that now and see if it works. – BSull Sep 28 '12 at 18:04
  • Much appreciated. Thanks. I did come across another error though. SHould -m32 be added before or after the code file? – BSull Sep 28 '12 at 18:10
  • let us [continue this discussion in chat](http://chat.stackoverflow.com/rooms/17308/discussion-between-bsull-and-rob) – BSull Sep 28 '12 at 18:12
0

I've recently suffer this problem using an automatic builder, namely drone.io.

The problem was that gcc in Ubuntu 12.04 was linking by default with -Wl,--as-needed. In my case, the project was using autotools, which means I was too lazy to write anything to modify the compilation order. Instead, modifying as-needed flag fixed the problem.

-gabriel_LDFLAGS = $(GLIB2_LIBS) $(DBUS_LIBS) -lssh
+gabriel_LDFLAGS = -Wl,--no-as-needed $(GLIB2_LIBS) $(DBUS_LIBS) -lssh

For full info, you can check the fixing commit in https://bitbucket.org/kikeenrique/gabriel/commits/f08eefdca3f7bb90f48f5a6fbfc8839422572508

You can take a look to the log with errors BEFORE applying the fix and also you can take a look to the log without errors AFTER applying the fix.

kikeenrique
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