TMS320C6748: Use a linker symbol in C code

Corentin NICOLAS

Part Number: TMS320C6748

Hello all !

With CCS v5 I would like to use in my C code a symbol named "start_symbol" declared as follows in my .cmd linker file

.my_section: align = 0x4 {} > l2_ram, START(start_symbol)

I would like to use this symbol in my C code as follows :

extern int start_symbol;

int my_function()
{
    int* var = &start_symbol;
    
    memset(var, 0, size);
}

but when linking, I got the following warnings:

warning #17009-D: relocation type is static ... relocation cannot be performed

and

warning #10015-D output file xxxx cannot be loaded and run on a target system.

Could you help please ?

Moreover, is there any detailed doc about .cmd file langage ?

Sincerly.

Corentin

over 2 years ago

0 Jianzhong Xu over 2 years ago

TI__Mastermind 40215 points

Hello Corentin,

Please refer to TI Linker Command File Primer.

One way to achieve what you need to do is to use the DATA_SECTION pragma. You can define a data section in your C code and place this section in the .cmd file.

C code:

#pragma DATA_SECTION(arr_x, ".section_arr_x");
int arr_x[SIZE_ARR];

Linker command file:

SECTIONS
{
    .section_arr_x > SHRAM
}

Please refer to TMS320C6000 Optimizing Compiler User's Guide regarding the DATA_SECTION pragma.

Regards,

Jianzhong

0 Corentin NICOLAS over 2 years ago in reply to Jianzhong Xu

Prodigy 40 points

Hello Jianzhong. Thanks for your response.

I've already created a section and placed data into it. What I want to realise is to create symbols from my .cmd file which indicate start and end of my section, in order to be able to realise an erase of the whole section. For this purpose, i've declared a section and used START(_sectionStart) and END(_sectionEnd).

I then use these symbols from my C code to do an erase. But in my C code, when i create pointer to these symbol as follows:

int* start = &sectionStart;
int* end = &sectionEnd;

i got warning as mentioned above. For the moment, i've noticed that if i delcare my pointer as "static", it works fine (it compiles, i've not tested on platform yet).

Thank you.

+1 George Mock over 2 years ago in reply to Corentin NICOLAS

TI__Guru**** 232630 points

The symbols created by the linker must be declared in C with the far keyword. For more details, please search the C6000 assembly tools manual for the sub-chapter titled Using Linker Symbols in C/C++ Applications.

Thanks and regards,

-George

0 Corentin NICOLAS over 2 years ago in reply to George Mock

Prodigy 40 points

Thanks for your response i think it responds to my questions ! Have a good day.

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TMS320C6748: Use a linker symbol in C code