TMS320C6748: RETAIN instruction

Nancy Wang

Expert 8210 points

Part Number: TMS320C6748

Hi,

CCSv8.2

TI compiler V8.2.4

The customer has implemented a mechanism similar to linux driver registration, the code is as follows：

typedef int (*func_t)(void);
#define D_PRAGMA(x) _Pragma(#x)

int vfs_yaffs2_init()
{
return 0;
}

func_t func_test = vfs_yaffs2_init;

D_PRAGMA( DATA_SECTION(func_test, ".env_reg") );
D_PRAGMA( RETAIN ( func_test ) );

Customer expects to put the pointer of the vfs_yaffs2_init function into the func_test variable, and use the RETAIN instruction to force the variable into the ".env_reg" data segment. He only needs to take out the pointer from the data segment to access the function.

When vfs_yaffs2_init is called in an external function, there is a func_test symbol in the map file. On the contrary, there is no func_test symbol in the map file.

Is it possible that when the function is not called externally, the compiler finds that in the above c file, no symbols are called externally, it ignores the RETAIN compilation instruction and directly optimizes the entire c file？

But even turning the optimization off will not solve the problem.

How to solve the problem?

over 2 years ago

0 George Mock over 2 years ago

TI__Guru**** 232750 points

Please let me know whether adding the linker option --unused_section_elimination=off causes func_test symbol to remain in the build.

Thanks and regards,

-George

0 xu yang over 2 years ago in reply to George Mock

Prodigy 160 points

I find out the option,and turn it off,but func_test symbol is not remain neither.

i have the same code in other c file, and it worked. the key is there is a external called function,i guess.

0 George Mock over 2 years ago in reply to xu yang

TI__Guru**** 232750 points

I suspect something has gone wrong while linking. The only way to understand what happened is to reproduce it. Unfortunately, this means I have to ask for the full CCS project. Please zip up the project by following the directions in the article Sharing projects, then attach the zip file to your next post.

Thanks and regards,

-George

0 xu yang over 2 years ago in reply to George Mock

Prodigy 160 points

hi:

thanks for your replys.

here is the project,test1_lib is a lib for test1.

0654.test1.zip

"code1.c", "code2.c"and"code3.c",are almost the same.

but, there is no module_code1_init symbol.

in code3.c of test1, RETAIN is worked.

in code1.c of test1_lib, RETAIN is not worked.

so in code2.c of test1_lib, RETAIN should not worked too.but the code2_extern function is called in main.c of test1,so RETAIN worked.

now, i hope RETAIN is worked in code1.c of test1_lib, without any external called functions.

0 George Mock over 2 years ago in reply to xu yang

TI__Guru**** 232750 points

The problem is that the symbol module_code1_init is defined in a library. The RETAIN pragma never forces a function (or data variable) to be brought in from a library. To do that, use the linker option --undef_sym. In your specific case, add the option --undef_sym=module_code1_init. Here is a screen shot.

After I do that, I see these lines in the linker map file ...

c0400004  module_code1_init                                                   
c0400008  module_code2_init                                                   
c0400000  module_code3_init

To learn more about --undef_sym, please search for it in the C6000 assembly tools manual.

Thanks and regards,

-George

0 xu yang over 2 years ago in reply to George Mock

Prodigy 160 points

thanks a lot.

it is worked.

i have another question.

in my project, why module_code2_init symbol can be created, i did not use --undef_sym option,yet?

0 JohnS over 2 years ago in reply to xu yang

TI__Guru**** 159715 points

George is going to be out for a few days. Do you need an answer to this one before then? If so I can try to find someone else to help.

Regards,

John

0 xu yang over 2 years ago in reply to JohnS

Prodigy 160 points

i think i can wait George's back,tks.

0 George Mock over 2 years ago in reply to xu yang

TI__Guru**** 232750 points

xu yang said:
in my project, why module_code2_init symbol can be created, i did not use --undef_sym option,yet?

Because the function main, in the test1 executable project, and not the test1_lib library project, calls the function code2_extern. That causes the file code2.obj to be brought in from the library test1_lib.lib. The .text section in code2.obj defines the functions code2_extern and module_code2_init.

Thanks and regards,

-George

0 xu yang over 2 years ago in reply to George Mock

Prodigy 160 points

i got it,thanks a lot.

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TMS320C6748: RETAIN instruction