Order of the variables in the memory

Jingbin Niu

Prodigy 110 points

Hi,

Is there any Mechanism for the order of variables in the memory?

eg:

/*four global variable*/

int Vara;
int Varb;
int Varc;
int Vard;

how can I get a map file looks like:

0000cc40 Vara
0000cc41 Varb
0000cc42 Varc
0000cc43 Vard

it seems that, even I use the #pragma to put them in one mem section "section1", I can't design the order "VaraVarbVarcVard" in the memory.
#pragma DATA_SECTION(Vara,"section1");
#pragma DATA_SECTION(Varb,"section1");
#pragma DATA_SECTION(Varc,"section1");
#pragma DATA_SECTION(Vard,"section1");

so i use

#pragma DATA_SECTION(Vara,"section1");
#pragma DATA_SECTION(Varb,"section2");
#pragma DATA_SECTION(Varc,"section3");
#pragma DATA_SECTION(Vard,"section4");

and the sections one by one, then I can determin the order.

Is there any simple method to achieve this order?

Thanks

over 13 years ago

0 Roman Ermakov over 13 years ago

Expert 1150 points

why to you not to use struct?

0 AartiG over 13 years ago in reply to Roman Ermakov

TI__Guru**** 173310 points

Here is a related thread on the same topic: http://e2e.ti.com/support/development_tools/compiler/f/343/t/183419.aspx

0 Jingbin Niu over 13 years ago in reply to Roman Ermakov

Prodigy 110 points

Hi Roman, thanks a lot. Struct do determine the order.

0 Norman Wong over 13 years ago in reply to Jingbin Niu

Guru 26430 points

For what I gather, the C standard states that order must be maintained. The C++ standard does allow reordering on "plain old data". Neither the C nor the C++ standard enforce packing. There could be holes between variables. And compilers always have non-standard features or aggressive optimization. Another way to maintain order would be use an array or declare your variables in assembler. You'd probably have to do manually alignment in assembler. Order and packing are usually only required for protocols.

0 Jingbin Niu over 13 years ago in reply to AartiG

Prodigy 110 points

Hi AartiG, thanks for the helpful reply.

"Define all those variables in hand coded assembly." mentioned by Georgem in the link, is very useful for my application

0 Jingbin Niu over 13 years ago in reply to Norman Wong

Prodigy 110 points

Hi Norman, thanks a lot for your suggestion

I will do manually alignment in assembler.

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Order of the variables in the memory