function declare

[Jython]

so it is rtems build requirement?

On Thu, Jun 27, 2019 at 2:53 AM Mr. Andrei Chichak <groups at chichak.ca>
wrote:

> Assume that you are using C and C has a facility to bind together object
> modules from different files.
>
> You define a function in one file, it has a bunch of parameters and
> doesn’t return anything.
>
> In another file you use that function but don’t have a prototype that
> tells the compiler anything about the function.
>
> Now assume that the compiler was written in 1972, and doesn’t benefit from
> things like mind reading.
>
> C assumes, by default, that *a function has one integer parameter and
> returns an integer, unless otherwise told*. What other choices has it
> got? Nothing really.
>
> So in later versions of C, they introduced a thing called a prototype that
> gives the compiler a hint about the parameters and return values of a
> function.
>
> All that you needed was to take your function header, put a semicolon on
> the end and paste it before the call to the function and the compiler would
> have done what you wanted instead of what you said.
>
> Better yet, take that prototype and put it into a header file and whenever
> you want to call the function, put in an include statement, the compiler
> get’s the information about the parameters and return values, and overrides
> the *int func( int)* default nature.
>
> A
>
> On 2019-June-26, at 12:41 AM, Jython <googcheng at gmail.com> wrote:
>
> I have a function named  *oled_write_temp* in a.c, if i dont declare it
> in a.h , then i will get the wrong supply value in the function within main
> call, why?
>
> if i  declare it in a.h, then all is right
>
> void oled_write_temp(float set_temp, const float supply, float return_temp)
>> {
>>
>>     int base_x = 12, base_y = 60;
>>
>>     char buffer[20] = {0};
>>
>>     *printf("supply_temp %f at %s\n", supply, __FUNCTION__);*
>>
>>     snprintf(buffer, 20, "SUPPLY:%.2f", supply);
>>     printf("supply_temp string %s\n", buffer);
>>
>>     oled_clear_area(base_x, base_y + 16, 122, base_y + 32);
>>     OLED_ShowString(base_x, base_y + 16, buffer, 16, 1);
>>
>>     memset(buffer, 0, sizeof(buffer));
>>     snprintf(buffer, 20, "RETURN:%.2f", return_temp);
>>     OLED_ShowString(base_x, base_y + 36, buffer, 16, 1);
>>
>>     memset(buffer, 0, sizeof(buffer));
>>     snprintf(buffer, 20, "SET   :%.2f", set_temp);
>>     OLED_ShowString(base_x, base_y + 56, buffer, 16, 1);
>>
>> }
>>
>
> ps: watch line  *printf("supply_temp %f at %s\n", supply, __FUNCTION__);*
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