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From:	Martin Ambuhl <mambuhl AT earthlink DOT net>
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Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: problem with return
References:	<1ed DOT 3702603c DOT 2f5a12e3 AT cs DOT com>
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Date:	Fri, 04 Mar 2005 21:04:37 GMT
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To:	djgpp AT delorie DOT com
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KTrumpetsRule AT cs DOT com wrote:
> I have a problem I'm having a really tough time tracking down.  Below is the
> code.  out_xxxx.c calls function cyl_volume() which is in bm_xxxx.c.  As I go
> along, I'm checking all the results against a Texas Instruments TI-30Xa
> calculator.

Your posted code (at EOM) is *not* the real code you use.
After making your code into a legal portable program (below), I cannot 
reproduce your problem:

[ An attempt to make the code compilable]
#include <stdio.h>
#include <math.h>

#define PI      3.14159265358979323846L

typedef struct
{
     double bore, stroke;
     double V_1_ci;
} engine_t;

double cyl_volume(engine_t *);

int main(void)
{
     double temp;
     engine_t eng = { 2.975, 3.23, 0 }, sim = {
     0, 0, 0};
     engine_t *psim = &sim;
     temp = 1102290688.;
     printf("psim->V_1_ci = %10.6f, temp = %10.6f\n", psim->V_1_ci,
            temp);
     temp = cyl_volume(&eng);
     psim->V_1_ci = temp;
     printf("CYLINDER VOLUME - %10.6f cubic inches\n", psim->V_1_ci);
     return 0;
}

double cyl_volume(engine_t * peng)
{
     double cyl_vol = 0.0;
     double temp1 = 0.0, temp2 = 0.0, temp3 = 0.0;

     cyl_vol = PI * (pow(peng->bore / 2, 2)) * peng->stroke;

     printf("inside cyl_volume()\n");
     printf("peng->bore = %10.6f, peng->stroke = %10.6f\n",
            peng->bore, peng->stroke);
     printf
         ("peng->bore/2 = %10.6f, pow(peng->bore/2, 2) = %10.6f\n",
          peng->bore / 2, pow(peng->bore / 2, 2));
     printf("PI = %10.10Lf, cyl_vol = %10.6f\n", PI, cyl_vol);
     temp1 = pow(peng->bore / 2, 2);
     temp2 = temp1 * peng->stroke;
     temp3 = temp2 * PI;
     printf("temp1 = %10.6f, temp2 = %10.6f, temp3 = %10.6f\n\n", temp1,
            temp2, temp3);
     return temp3;


}

[output from this program]
psim->V_1_ci =   0.000000, temp = 1102290688.000000
inside cyl_volume()
peng->bore =   2.975000, peng->stroke =   3.230000
peng->bore/2 =   1.487500, pow(peng->bore/2, 2) =   2.212656
PI = 3.1415926536, cyl_vol =  22.452585
temp1 =   2.212656, temp2 =   7.146880, temp3 =  22.452585

CYLINDER VOLUME -  22.452585 cubic inches


[original poster's "code"]
> THIS IS IN OUT_XXXX.C
> /*
>     locate(5,5);
>     printf("Computing CYLINDER VOLUME ... ");
> */
>     temp = 0.0;
>     temp = cyl_volume(&eng_0);
>     locate(5,5);
>     printf("ptr_sim_0->V_1_ci = %10.6f, temp = %10.6f",
>         ptr_sim_0->V_1_ci, temp);
>     locate(13,5);
>     ptr_sim_0->V_1_ci = cyl_volume(&eng_0);         /*  this is in bm_xxxx.c    
> */
>     locate(13,5);
>     printf("CYLINDER VOLUME - %10.6f cubic inches", ptr_sim_0->V_1_ci);
>     pause(0);
> 
> THIS IS IN BM_XXXX.C
> float cyl_volume(ENGINE *ptr_eng_0)
> {
>     float cyl_vol = 0.0;
>     float temp1 = 0.0, temp2 = 0.0, temp3 = 0.0;
> 
>     cyl_vol = PI * (pow(ptr_eng_0->bore/2, 2)) *
>                 ptr_eng_0->stroke;
> 
> /* start debug */
>     locate(7,5);
>     printf("inside cyl_volume()");
>     locate(8,5);
>     printf("ptr_eng_0->bore = %10.6f, ptr_eng_0->stroke = %10.6f",
>         ptr_eng_0->bore, ptr_eng_0->stroke);
>     locate(9,5);
>     printf("ptr_eng_0->bore/2 = %10.6f, pow(ptr_eng_0->bore/2, 2) = %10.6f",
>         ptr_eng_0->bore/2, pow(ptr_eng_0->bore/2, 2));
>     locate(10,5);
>     printf("PI = %10.10f, cyl_vol = %10.6f", PI, cyl_vol);
>     locate(11,5);
>     temp1 = pow(ptr_eng_0->bore/2, 2);
>     temp2 = temp1 * ptr_eng_0->stroke;
>     temp3 = temp2 * PI;
>     printf("temp1 = %10.6f, temp2 = %10.6f, temp3 = %10.6f", temp1, temp2, 
> temp3);
>     return temp3;
> /* end debug */
> 
>     /* return cyl_vol; */
> }
> 
> THIS IS RESULTS ON SCREEN
>   ptr_sim_0->V_1_ci =   0.000000, temp = 1102290688.000000
> 
>   inside cyl_volume())
>   ptr_eng_0->bore =   2.975000, ptr_eng_0->stroke =   3.230000
>   ptr_eng_0->bore/2 =   1.487500, pow(ptr_eng_0->bore/2, 2) =   2.212656
>   PI = 3.1415927000, cyl_vol =  22.452583
>   temp1 =   2.212656, temp2 =   7.146879, temp3 =  22.452583
> 
>   CYLINDER VOLUME - 1102290688.000000 cubic inches
> 
> As you can see from the section titles "THIS IS RESULTS ON SCREEN" even though
> temp3 contains the correct value, it doesn't seem to be returned as such.  All
> assigned values and computed values check out OK within the cyl_volume()
> function.  Again, this is shown by the "RESULTS" screen.
> 
> Any help would be appreciated.
> 
[Obscenely oversize sig (without sig separator) removed]

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