GCC Compile Problem (link)

Hi all,
Really to say I'm not very familar with C and esspecially with C in linux-based systems, bcz. have spent 6 years in C# programming. But now, I'm back to C :). So I need your experience help.

Here is the problem: I cannot compile the C project (DiskSim) because recieve the following error: "undefined reference to `sqrt'"
But the main problem is that in makefile THERE IS link flag -lm to math.h

Any ideas?

My system:
ubuntu 11.10 x64
gcc, g++ 4.6
flex, bison 2.5
KDevelop as IDE

I have attached the error log file, the makefile. (let me know if you need the whole project - but it is about 5 Mb)

Thanks a lot for any help.
Best,
Timbuktu

You need to link the mathematics library. Make sure you're including <math.h>, and that you compile thusly:

Code:

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gcc -o myprog myprog.c -lm

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the GNU linker doesn't do multiple passes until you tell it to. and since you linked your library mems_internals after -lm, the linker did not pull the math functions. look in the gnu linker documentation for --startgroup/--endgroup OR maybe you can just put -lm after your library.

Thanks all for the replay,

both is already done, but with no effect

<math.h> is in the .c file
-lm after the library also take nothing

Another tipp?

Quote:

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Originally Posted by Timbuktu

<math.h> is in the .c file
-lm after the library also take nothing

---

Do you mean it's at the end of the line:

Code:

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$(CC) -o $@ mems_seektest.o $(LDFLAGS) $(CFLAGS) -lmems_internals

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Because it'll need to be if libmems_internals relies on libm.

Otherwise, please post the command-line make ends up issuing.

Not sure I correct understand you.

I have just put the -lm at the end of the line. The result is 100% the same.

So look this line now:

$(CC) -o $@ mems_seektest.o $(CFLAGS) -lmems_internals $(LDFLAGS)