Linker error : no definition for "DATA"(variable of type struct data_t)

[youssef.amimi]

I have declared a typedef struct data_t on my jsmn.h

after that I declared a variable DATA of type data_t on jsmn.c

and i defined N,T,C and H

then i declared DATA of type Data_t as extern on ScreenViewBase.cpp

and i try to display DATA.N on the screen

but a linker error appear : no definition for DATA referenced from ScreenViewBase.o

PS1: I do the same with time : in ScreenViewBase.cpp I declared extern RTC_TimeTypeDef sTime then  I write Unicode::snprintf(Ndata, 6, "%02d",sTime.Hours ); and it work perfectly.

PS2: I work with stm32f769 and with IAR 8.32.3

[Tesla DeLorean]

Perhaps because DATA isn't very original, and is used as a variable or section name within the namespace of the project, or associated libraries.

Pick something more unique...

[youssef.amimi]

Hi @Community member​ 

I tried that(I replaced with youssef_data) but steel the same problem

[Tesla DeLorean]

Are we sure this is a linker error?

Post a build log, saves playing guess what's wrong.

[youssef.amimi]

this is a screenshot of the build log

[Tesla DeLorean]

Kind of suggests

a) jsmn.c isn't in the project

b) The mixing of C/CPP compilation results in name mangling on the C++ side, and thus an inability to find the symbol

Perhaps use

extern "C" Data_t DATA;

[youssef.amimi]

a) jsmn.c is in the project.

b) I used extern "C" , but the same problem.

[Tesla DeLorean]

The linker seems to disagree, perhaps you need to disassemble the objects and see what symbols are actually inside them.

Not sure if the IAR linker outputs a .MAP on failure cases, or if there are options for verbose output, etc.

[youssef.amimi]

@Community member​ 

I don't know why but when I add this line (Data_t DATA); in main.cpp the error disappear.

[youssef.amimi]

I know now what is the problem the Data_t DATA was declared localy on a function in jsmn.c , I declare Data_t DATA globally and I elimineted this declaration in main.cpp