NO_INIT_BSS

Prevents initializing a BSS section to zero to avoid uninitialized variable to be iniatialized to zero by the startup.

NO_INIT_BSS
  

If the variable is initialized to 0 while using the directive NO_INIT_BSS then the variable will be placed in BSS section and will not be initialized to zero ( NO_INIT_BSS Directive Usage - Example 1).

Following are few examples of using the NO_INIT_BSS directive.

LCF:
.......

    GROUP : {    

       .__uninitialized_intc_handlertable ALIGN(0x10) : {}

       .data   : {}

       .user_def_Init (DATA):{}

       .sdata  : {}

       .sbss   : {}

       .sdata2 : {}

       .sbss2  : {}

       .bss    : {}

      .user_def_Uninit (BSS) NO_INIT_BSS :{}

    } > internal_ram

.......



Test case:

#pragma section RW ".user_def_Init" ".user_def_Uninit"           

// first user defined section treated as initialized section and second   

// user defined section treated as uninitialized section

__declspec (section ".user_def_Init")  int myvar_a;         

// myvar_a  goes to user_def_Uninit section as it is not initialized

__declspec (section ".user_def_Init")  int myvar_b=3;     

// myvar_b  goes to user_def_Init section as it is initialized

__declspec (section ".user_def_Init")  int myvar_c=0;     

// myvar_c goes to user_def_Init section as it is initialized to zero

// But var myvar_c is not initialized to zero as it comes under 
NO_INIT_BSS



int main(void) {

  volatile int i = 0;



  /* Loop forever */

  for (;;) {

    i++;

    myvar_a ++;

    myvar_b ++;

  }

}

LCF:
.......

    GROUP : {    

       .__uninitialized_intc_handlertable ALIGN(0x10) : {}

       .data   : {}

       .user_def_Init (DATA):{}

       .sdata  : {}

       .sbss   : {}

       .sdata2 : {}

       .sbss2  : {}

       .bss    : {}

      .user_def_Uninit (BSS) NO_INIT_BSS :{}

    } > internal_ram

.......

Test case:

#pragma push //Save the original pragma context 

#pragma section data_type sdata_type ".user_def_Init" 
".user_def_Uninit" 

unsigned int test_var; //Here variable test_var will place in the 
section user_def_Uninit and NOT initializes to zero. 

#pragma pop

unsigned int test_var2 = 0; //Here variable test_var2 will place in 
.bss/.sbss section and initializes to zero.

LCF:
.......

    GROUP : {    

       .__uninitialized_intc_handlertable ALIGN(0x10) : {}

       .data   : {}

       .user_def_Init (DATA):{}

       .sdata  : {}

       .sbss   : {}

       .sdata2 : {}

       .sbss2  : {}

       .bss    : {}

      .user_def_Uninit (BSS) NO_INIT_BSS :{}

    } > internal_ram

.......

Test case:

#pragma push //Save the original pragma context 

#pragma section data_type sdata_type ".user_def_Init" 
".user_def_Uninit" 

unsigned int test_var; // Variable test_var will place in the section 
user_def_Uninit

#pragma explicit_zero_data on

unsigned int test_var2 = 0; // Variable test_var2 will place in the 
section user_def_Init as the pragma // explicit_zero_data is enabled

#pragma explicit_zero_data reset                                           
(OR #pragma explicit_zero_data off)

unsigned int test_var3 = 5; //Variable test_var3 will place in the 
section user_def_Init

unsigned int test_var4 = 0; //Variable test_var3 will place in the 
section user_def_Uninit

#pragma pop