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tony5429

Member

Registered: 2006-03-28

Posts: 1,017

GCC Math.h Support Broken?? [SOLVED]

My source code:

#include <stdio.h>
#include <math.h>

int main(void) {
    float x, y;
    y = 5;
    x = log(y);
    printf("%f\n", x);
    return 0;
}

Running GCC:

bash-3.2# gcc -o /usr/bin/testlog /home/karam/testlog.c
/tmp/ccC4o2tO.o: In function `main':
testlog.c:(.text+0x19): undefined reference to `log'
collect2: ld returned 1 exit status

Running GCC with the verbose tag:

Using built-in specs.
Target: x86_64-unknown-linux-gnu
Configured with: ../configure --prefix=/usr --enable-shared --enable-languages=c,c++,fortran,objc,obj-c++,treelang --enable-threads=posix --mandir=/usr/share/man --enable-__cxa_atexit --disable-multilib --libdir=/usr/lib --libexecdir=/usr/lib --enable-clocale=gnu --disable-libstdcxx-pch --with-tune=generic
Thread model: posix
gcc version 4.3.0 (GCC)
COLLECT_GCC_OPTIONS='-o' '/usr/bin/testlog' '-v' '-mtune=generic'
 /usr/lib/gcc/x86_64-unknown-linux-gnu/4.3.0/cc1 -quiet -v /home/karam/testlog.c -quiet -dumpbase testlog.c -mtune=generic -auxbase testlog -version -o /tmp/cccPgY2e.s
ignoring nonexistent directory "/usr/lib/gcc/x86_64-unknown-linux-gnu/4.3.0/../../../../x86_64-unknown-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:
 /usr/local/include
 /usr/lib/gcc/x86_64-unknown-linux-gnu/4.3.0/include
 /usr/lib/gcc/x86_64-unknown-linux-gnu/4.3.0/include-fixed
 /usr/include
End of search list.
GNU C (GCC) version 4.3.0 (x86_64-unknown-linux-gnu)
        compiled by GNU C version 4.3.0, GMP version 4.2.2, MPFR version 2.3.1.
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
Compiler executable checksum: f09caaaff33a7d24655f4bdc6a5a8cad
COLLECT_GCC_OPTIONS='-o' '/usr/bin/testlog' '-v' '-mtune=generic'
 as -V -Qy -o /tmp/ccuax4mo.o /tmp/cccPgY2e.s
GNU assembler version 2.18 (x86_64-unknown-linux-gnu) using BFD version (GNU Binutils) 2.18
COMPILER_PATH=/usr/lib/gcc/x86_64-unknown-linux-gnu/4.3.0/:/usr/lib/gcc/x86_64-unknown-linux-gnu/4.3.0/:/usr/lib/gcc/x86_64-unknown-linux-gnu/:/usr/lib/gcc/x86_64-unknown-linux-gnu/4.3.0/:/usr/lib/gcc/x86_64-unknown-linux-gnu/:/usr/lib/gcc/x86_64-unknown-linux-gnu/4.3.0/:/usr/lib/gcc/x86_64-unknown-linux-gnu/
LIBRARY_PATH=/usr/lib/gcc/x86_64-unknown-linux-gnu/4.3.0/:/usr/lib/gcc/x86_64-unknown-linux-gnu/4.3.0/:/usr/lib/gcc/x86_64-unknown-linux-gnu/4.3.0/../../../../lib/:/lib/../lib/:/usr/lib/../lib/:/usr/lib/gcc/x86_64-unknown-linux-gnu/4.3.0/../../../:/lib/:/usr/lib/
COLLECT_GCC_OPTIONS='-o' '/usr/bin/testlog' '-v' '-mtune=generic'
 /usr/lib/gcc/x86_64-unknown-linux-gnu/4.3.0/collect2 --eh-frame-hdr -m elf_x86_64 --hash-style=both -dynamic-linker /lib/ld-linux-x86-64.so.2 -o /usr/bin/testlog /usr/lib/gcc/x86_64-unknown-linux-gnu/4.3.0/../../../../lib/crt1.o /usr/lib/gcc/x86_64-unknown-linux-gnu/4.3.0/../../../../lib/crti.o /usr/lib/gcc/x86_64-unknown-linux-gnu/4.3.0/crtbegin.o -L/usr/lib/gcc/x86_64-unknown-linux-gnu/4.3.0 -L/usr/lib/gcc/x86_64-unknown-linux-gnu/4.3.0 -L/usr/lib/gcc/x86_64-unknown-linux-gnu/4.3.0/../../../../lib -L/lib/../lib -L/usr/lib/../lib -L/usr/lib/gcc/x86_64-unknown-linux-gnu/4.3.0/../../.. /tmp/ccuax4mo.o -lgcc --as-needed -lgcc_s --no-as-needed -lc -lgcc --as-needed -lgcc_s --no-as-needed /usr/lib/gcc/x86_64-unknown-linux-gnu/4.3.0/crtend.o /usr/lib/gcc/x86_64-unknown-linux-gnu/4.3.0/../../../../lib/crtn.o
/tmp/ccuax4mo.o: In function `main':
testlog.c:(.text+0x19): undefined reference to `log'
collect2: ld returned 1 exit status

Last edited by tony5429 (2008-04-26 14:45:30)

winch

Member

Registered: 2008-04-13

Posts: 43

Re: GCC Math.h Support Broken?? [SOLVED]

You also need to tell gcc to link with the math library.

gcc -o /usr/bin/testlog /home/karam/testlog.c -lm

Last edited by winch (2008-04-21 19:06:41)

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github

tony5429

Member

Registered: 2006-03-28

Posts: 1,017

Re: GCC Math.h Support Broken?? [SOLVED]

It worked; thanks!

g_SG

Member

From: São Carlos/SP, Brazil

Registered: 2009-01-20

Posts: 11

Website

Re: GCC Math.h Support Broken?? [SOLVED]

The -lm flag works, but is there I way to let gcc do it automatically? I use Vim and gcc manually at home, but my professor wants us to use Netbeans in class, and it won't compile because of that.

GogglesGuy

Member

From: Rocket City

Registered: 2005-03-29

Posts: 610

Website

Re: GCC Math.h Support Broken?? [SOLVED]

The -lm flag works, but is there I way to let gcc do it automatically? I use Vim and gcc manually at home, but my professor wants us to use Netbeans in class, and it won't compile because of that.

You mean it won't link.
No. GCC doesn't have a crystal ball to guess which libraries you need.

caelestis

Member

Registered: 2009-04-04

Posts: 88

Re: GCC Math.h Support Broken?? [SOLVED]

Why not? Why isn't #include <math.h> good enough?

djgera

Developer

From: Buenos Aires - Argentina

Registered: 2008-12-24

Posts: 723

Website

Re: GCC Math.h Support Broken?? [SOLVED]

The -lm flag works, but is there I way to let gcc do it automatically? I use Vim and gcc manually at home, but my professor wants us to use Netbeans in class, and it won't compile because of that.

Can use make? So can generate a simple Makefile

HashBox

Member

Registered: 2009-01-22

Posts: 271

Re: GCC Math.h Support Broken?? [SOLVED]

I find it hard to believe that Netbeans wouldn't have a method of defining linker arguments, have you looked around for something like that?

dagle

Member

Registered: 2009-01-04

Posts: 13

Re: GCC Math.h Support Broken?? [SOLVED]

Why not? Why isn't #include <math.h> good enough?

For building but not for linking.

Lexion

Member

Registered: 2008-03-23

Posts: 510

Re: GCC Math.h Support Broken?? [SOLVED]

lol I just got this error today! Use -lm for linking: 'gcc allyourobjfiles.o -o exefile -lm'

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urxvtc / wmii / zsh / configs / onebluecat.net
Arch will not hold your hand

fumbles

Member

Registered: 2006-12-22

Posts: 246

Re: GCC Math.h Support Broken?? [SOLVED]

.

Last edited by fumbles (2020-09-26 11:44:03)

g_SG

Member

From: São Carlos/SP, Brazil

Registered: 2009-01-20

Posts: 11

Website

Re: GCC Math.h Support Broken?? [SOLVED]

The -lm flag works, but is there I way to let gcc do it automatically? I use Vim and gcc manually at home, but my professor wants us to use Netbeans in class, and it won't compile because of that.

Can use make? So can generate a simple Makefile

True! That's so obvious I'm ashame I didn't think about it. Thanks!