No, it has nothing to do with RTEMS in particular. Any C program will do this.
> On 2019-June-27, at 21:17, Jython <googch...@gmail.com> wrote: > > so it is rtems build requirement? > > On Thu, Jun 27, 2019 at 2:53 AM Mr. Andrei Chichak <gro...@chichak.ca > <mailto:gro...@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 <googch...@gmail.com >> <mailto:googch...@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__); >> _______________________________________________ >> users mailing list >> users@rtems.org <mailto:users@rtems.org> >> http://lists.rtems.org/mailman/listinfo/users >> <http://lists.rtems.org/mailman/listinfo/users> >
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