🚀 go-pugleaf

Chano Gómez Martínez (chano@ran.es) wrote:
: First of all, I want to apologize for my awful English.

: I'm trying to port a C program from Borland C++ 3.1 to GCC under
: Linux.
: My problem is that I can't use any function from math.h !!!
: The file is correctly #include'd ( in fact, I get no compilation
: errors ) but the linker always tells me something like :
snip
Your English is impeccable.  I expect your only problem with gcc is that 
you've neglected to link the math library by typing -lm when you invoke 
gcc.  I use cc to compile and link my ANSI C programs developed in Turbo 
C 3.1 with the following command: 
cc MyProg.c -lm -O
I expect gcc is the same.
Toby Hay    thay@uoguelph.ca

In article <4l1and$iql@news.ran.es>,
   chano@ran.es (Chano Gómez Martínez) wrote:
-First of all, I want to apologize for my awful English.
-
-Now, the C stuff :
-
-I'm trying to port a C program from Borland C++ 3.1 to GCC under
-Linux.
-My problem is that I can't use any function from math.h !!!

Try -lm on the link line.  The problem is that libm.a (the math library) is 
not being linked into your program, so no math functions are resolved.  You 
may also have to tell the linker where libm.a is located if it isn't in one of 
the standard places.

In article <4l1and$iql@news.ran.es>, chano@ran.es (Chano Gómez Martínez) wrote:

> First of all, I want to apologize for my awful English.
> 
> Now, the C stuff :
> 
> I'm trying to port a C program from Borland C++ 3.1 to GCC under
> Linux.
> My problem is that I can't use any function from math.h !!!
> The file is correctly #include'd ( in fact, I get no compilation
> errors ) but the linker always tells me something like :
> 
> /tmp/cca000971.o(.text+0x39): undefined reference to `exp'
> 
> The funny thing is that GPC ( the GNU Pascal compiler ) allows me to
> use math.h functions lihe exp(), sin(), fabs(), etc, but when I
> convert my Pascal programs to C with p2c and try to compile them with
> GCC , I get the same error again.
> 
<<<deletia regarding GPC and gcc>>>
> 
> The only apparent difference between both results is in the libraries
> ( I think)
> Can anyone help me, please ???
> 

Yes, the difference is in the libraries.  To use exp, sin, ...
you need to include '-lm' (at least on your system) in the invoking 'gcc'
line.  The GPC thing had it already included.  Most functions in <math.h>
need the '-lm' addition if compiled under a Unix style compiler.  This is
probably an FAQ! (see the C faq's on the friendly 'rtfm' server).

-- 
Tom Watson
tsw@3do.com         (Home: tsw@johana.com)

Chano Gómez Martínez wrote:
> 
[snip]
> 
> /tmp/cca000971.o(.text+0x39): undefined reference to `exp'
> 
> The funny thing is that GPC ( the GNU Pascal compiler ) allows me to
> use math.h functions lihe exp(), sin(), fabs(), etc, but when I
> convert my Pascal programs to C with p2c and try to compile them with
> GCC , I get the same error again.

are you linking in the math library?
$ gcc file.c -o file -lm

[snip]

-- 
Glenn Lamb
System's Administrator
glenn@sec.sel.sony.com

Chano Gómez Martínez wrote:
> 
> First of all, I want to apologize for my awful English.

  I should say the same ;^)

> Now, the C stuff :
> 
> I'm trying to port a C program from Borland C++ 3.1 to GCC under
> Linux.
> My problem is that I can't use any function from math.h !!!
> The file is correctly #include'd ( in fact, I get no compilation
> errors ) but the linker always tells me something like :
> 
> /tmp/cca000971.o(.text+0x39): undefined reference to `exp'
> 
> The funny thing is that GPC ( the GNU Pascal compiler ) allows me to
> use math.h functions lihe exp(), sin(), fabs(), etc, but when I
> convert my Pascal programs to C with p2c and try to compile them with
> GCC , I get the same error again.
> 
> Here is the result from compiling the Pascal source with GPC -v ...
> ================================================
>
(...messages from gpc...)

> -L/usr/i486-linux/lib /tmp/cca001031.o -lgpc -lgcc -lm -lc -lg
Here it is!                                         ^^^^^^

(...messages from gcc...)
>
> The only apparent difference between both results is in the libraries
> ( I think)
> Can anyone help me, please ???
> 

When you compile some code, you need to link it to the right libraries.
For instance, you need to link your program with the library libm which
is for math.
Try `gcc ... -lm`. In general, for foo.h try -lfoo, but you'd better
check /lib or /usr/lib.

>    Thanks in advance.
Hope this helps :)

-- 
Christophe Juniet 
chris@lmm.com 
Un Linux, s'il vous plaît!
(A Linux, please!)