Re: Problem compiling simple C program

John Salmon wrote:
Sven Joachim <svenjoac@xxxxxx> wrote in news:aiYRm-2Tc-23@xxxxxxxxxxxxxxxx:

On 2008-04-15 20:39 +0200, John Salmon wrote:

I'm running Debian Etch on a PC. When I try to compile the following (called test.c);

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

int main()
{
double
val = 1.55;

printf("sine: %g\n", sin(val));

return 0;
}

using the command line

gcc -Wall -o test test.c

I get

/tmp/cciDV02m.o: In function `main':
test.c:(.text+0x21): undefined reference to `sin'
collect2: ld returned 1 exit status
You need to link to the math library by specifying -lm _at the end_ of
the gcc command line, otherwise the linker does not know about the sin()
function.

When I compile the equivalent C++ program using the apropriate C++ parameters, everything goes great. Have I neglected to load a Debian package? Any help will be appreciated.
That is to be expected, because C++ programs are automatically linked
against the math library. In C you have to tell the linker to use it
with -lm.

Sven



That solved the linking problem. Now, after a successful compilation, when I run 'test' I gen no output. ???


In the directory where you source and output executable is, try "./test".

You are not getting any output probably because you are inadvertently using the system "test" command.

To avoid such introduction traps, I usually make such example programs with names quite different from any commands that the system may have, for example by using my initials or by using a number in the source file. Using "mytest" or "example1" would have been a better choice in your case.

->HS


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