[ale] Missing "floor"?

[leam hall]

Ed, thanks!

Oddness, the RHEL 5 box I'm on needs the -lm option. Of course, it would be
nice for them to pick options that are easy to tell if they are numbers or
characters.  :(

Leam


On Wed, Jun 19, 2013 at 12:02 PM, Ed Cashin <ecashin at noserose.net> wrote:

> Yes, ignoring stuff like inline functions defined in headers, standard
> UNIX-like expectations would be for the header math.h to contain a function
> *prototype* that *declares* floor.
>
> The library contains the compiled floor function *definition* as
> executable code for your architecture.  The source for the definition is
> part of glibc, probably a function body *defined* in a .c file.
>
> Both the source and the compiled form of the function can be thought of as
> the implementation in different forms.  The declaration in the header is
> information that the compiler can use to make sure that the types of the
> function parameters and of the return value are right.  You can think of
> the header stuff as "interface" as opposed to "implementation", but the C
> language and runtime aren't essentially modular, so you'll exhaust the
> usefulness of that metaphor if you go very deep.
>
> Usually the specific difference is the compiler option Sparr mentions.
>  You can see that on the CentOS 6 system I'm using, the option isn't
> required:
>
> [ecashin at marino ~]$ cat > t.c
> #include <math.h>
> #include <stdio.h>
>
> int main(void)
> {
>         printf("%g\n", floor(2.3));
>         return 0;
> }
> [ecashin at marino ~]$ gcc -Wall t.c
> [ecashin at marino ~]$ ./a.out
> 2
> [ecashin at marino ~]$ gcc -Wall t.c -lm
> [ecashin at marino ~]$ ./a.out
> 2
> [ecashin at marino ~]$
>
>
> On Wed, Jun 19, 2013 at 10:54 AM, Sparr <sparr0 at gmail.com> wrote:
>
>> math.h only declares the function. The implementation is in /var/lib/libm
>> (math lib). You need to tell the compiler to link to that with -lm
>> On Jun 19, 2013 10:52 AM, "leam hall" <leamhall at gmail.com> wrote:
>>
>>> Morning Ed!
>>>
>>> I'm looking around (googling) to understand what you mean and I'm not
>>> getting it. math.h is included in the program and exists in /usr/include.
>>>
>>> Leam
>>>
>>>
>>>
>>> On Wed, Jun 19, 2013 at 10:30 AM, Ed Cashin <ecashin at noserose.net>wrote:
>>>
>>>> Maybe link the math library?  A quick check suggests that's it.
>>>>
>>>> [ecashin at marino ~]$ man floor | grep Link
>>>>        Link with -lm.
>>>> [ecashin at marino ~]$
>>>>
>>>>  On Wed, Jun 19, 2013 at 10:18 AM, leam hall <leamhall at gmail.com>wrote:
>>>>
>>>>>  Not sure why I'm getting:
>>>>>
>>>>> gcc -Wall -Werror -o rand rand.c
>>>>> /tmp/ccAJ7e8S.o: In function `main':
>>>>> rand.c:(.text+0x16): undefined reference to `floor'
>>>>> collect2: ld returned 1 exit status
>>>>>
>>>>> ###
>>>>> rand.c
>>>>> ###
>>>>>
>>>>> #include <stdio.h>
>>>>> #include <unistd.h>
>>>>> #include <stdlib.h>
>>>>> #include <math.h>
>>>>>
>>>>> int main(void) {
>>>>>
>>>>>     int num;
>>>>>     float val = 2.3;
>>>>>     num = floor(val);
>>>>>     printf("num is %d.\n", num);
>>>>>
>>>>>     return 0;
>>>>> }
>>>>>
>>>>> --
>>>>> Mind on a Mission <http://leamhall.blogspot.com/>
>>>>>
>>>>> _______________________________________________
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>>>>>
>>>>>
>>>>
>>>
>>> --
>>> Mind on a Mission <http://leamhall.blogspot.com/>
>>>
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>
>
> --
>   Ed Cashin <ecashin at noserose.net>
>   http://noserose.net/e/
>   http://www.coraid.com/
>
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-- 
Mind on a Mission <http://leamhall.blogspot.com/>
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