6.1.1
C/C++ Program Sections
The correspondence between memory areas and sections for C/C++ programs and the standard library is described in Table 6.1.
Table 6.1 | Summary of Memory Area Types and Their Properties |
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1
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Program area
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P *1*6
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code
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Relative
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Yes
Not possible
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1 byte *7
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Stores machine code
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2
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Constant area
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C_8 *1 *2 *6 *8 *10
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romdata
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Relative
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Yes
Not possible
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8 bytes
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Stores const type data
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C *1*2*6*8
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romdata
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Relative
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Yes
Not possible
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4 bytes
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C_2 *1*2*6*8
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romdata
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Relative
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Yes
Not possible
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2 bytes
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C_1 *1*2*6*8
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romdata
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Relative
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Yes
Not possible
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1 byte
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3
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Initialized data area
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D_8 *1 *2 *6 *8 *10
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romdata
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Relative
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Yes
Possible
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8 bytes
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Stores data with initial values
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D *1*2*6*8
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romdata
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Relative
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Yes
Possible
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4 bytes
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D_2 *1*2*6*8
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romdata
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Relative
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Yes
Possible
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2 bytes
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D_1 *1*2*6*8
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romdata
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Relative
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Yes
Possible
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1 byte
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4
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Uninitialized data area
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B_8 *1 *2 *6 *8 *10
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data
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Relative
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No
Possible
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8 bytes
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Stores data without initial values
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B *1*2*6*8
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data
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Relative
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No
Possible
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4 bytes
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B_2 *1*2*6*8
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data
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Relative
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No
Possible
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2 bytes
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B_1 *1*2*6*8
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data
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Relative
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No
Possible
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1 byte
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5
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switch statement branch table area
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W *1*2
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romdata
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Relative
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Yes
Not Possible
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4 bytes
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Stores branch tables for switch statements
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W_2 *1*2
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romdata
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Relative
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Yes
Not Possible
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2 bytes
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W_1 *1*2
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romdata
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Relative
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Yes
Not Possible
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1 byte
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6
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C++ initial processing/ postprocessing data area
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C$INIT
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romdata
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Relative
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Yes
Not possible
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4 bytes
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Stores addresses of constructors and destructors called for global class objects
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7
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C++ virtual function table area
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C$VTBL
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romdata
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Relative
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Yes
Not possible
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4 bytes
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Stores data for calling the virtual function when a virtual function exists in the class declaration
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8
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User stack area
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SU
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data
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Relative
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No
Possible
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4 bytes
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Area necessary for program execution
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9
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Interrupt stack area
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SI
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data
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Relative
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No
Possible
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4 bytes
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Area necessary for program execution
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10
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Heap area
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-
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-
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Relative
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No
Possible
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-
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Area used by library functions malloc, realloc, calloc, and new *9
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11
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Absolute address variable area
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$ADDR_
<section>_
<address>
*3
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data
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Absolute
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Yes/No
Possible/
Not possible *4
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-
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Stores variables specified by #pragma address
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12
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Variable vector area
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C$VECT
C$VECT<vector table number>
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romdata
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Relative
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No
Possible
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4 bytes
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Variable vector table
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13
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Literal area
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L *5
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romdata
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Relative
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Yes
Possible/
Not possible
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4 bytes
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Stores string literals and initializers used for dynamic initialization of aggregates
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Notes 1. | Section names can be switched using the section option. |
Notes 2. | Specifying a section with a boundary alignment of 4 when switching the section names also changes the section name of sections with a boundary alignment of 1, 2, or 8. |
Notes 3. | <section> is a C, D, or B section name, and <address> is an absolute address (hexadecimal). |
Notes 4. | The initial value and write operation depend on the attribute of <section>. |
Notes 5. | The section name can be changed by using the section option. In this case, the C section can be selected as the changed name. |
Notes 6. | The section name can be changed through #pragma section. |
Notes 7. | Specifying the instalign4 or instalign8 option, #pragma instalign4, or #pragma instalign8 changes the boundary alignment to 4 or 8. |
Notes 8. | If an endian not matching the endian option has been specified in #pragma endian, a dedicated section is created to store the relevant data. At the end of the section name, _B is added for #pragma endian big, and _L is added for #pragma endian little. |
Notes 9. | Using these functions requires the allocation of at least 16 bytes of memory as a heap area. |
Notes 10. | This section is for storing double-precision floating-point data when the dpfpu option is specified. |
Examples 1. | A program example is used to demonstrate the correspondence between a C program and the compiler-generated sections. |
C program
int a=1;
char b;
const short c=0;
void main(){
...
}
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Program area (main(){...})
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P
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Constant area (c)
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C_2
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Initialized data area (a)
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D
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Uninitialized data area (b)
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B_1
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Examples 2. | A program example is used to demonstrate the correspondence between a C++ program and the compiler-generated sections. |
C++ program
class A{
int m;
A(int p);
~A();
};
A a(1);
char b;
extern const char c='a';
short d=1;
void f(){...}
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Program area (f(){...})
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P
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Constant area (c)
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C_1
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Initialized data area (d)
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D_2
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Uninitialized data area (a)
Uninitialized data area (b)
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B
B_1
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Initial processing/
postprocessing data areas (&A::A, &A::~A)
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C $INT
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