c中的内存占用部分

Question

could you explain what these section mean when you collect memory footprint in c? I can see .text is source code and I assume .const and .data are global data and constants(but not too sure) and what does .bss mean?

| .text    | .const    | .data     | .bss      |

Answer 1

Some answer you can find here . That covers also the run-time managed sections heap and stack (that was the original answer).

In short (an extended):

• .bss is for uninitialized variables declared static and with global scope. This is not actually stored in the file, but just reserved and cleared at run-time right before `main() is called.
• .data contains explicitly initialized variables.
• .const contains const declared objects.
• .text is where the program code is stored. Note that is not the source code, but the compiled program code!

There is also a plethora of other sections in normal "ELF" object files which contain debugging information, etc.

For more information, read about object file formats. One of the most widely used is ELF .

Answer 2

.bss is/are uninitialised static variables.

// foo ends up in bss (because it is not explicitly initialised)
// it's initial value is whatever the default 'zero' value for the type is.
static int foo;
// bar ends up in .data
// (because) it is initialised with the value 42. 
static int bar = 42;
// baz ends up in .const
// (because) it is initialised with a value (22) and the object is const.
// meaning that the value cannot be allowed to change, meaning the object
// can be safely mapped to read-only memory pages (if supported).
static const int baz = 22;
// code goes in .text:
int main() { return 0; }

Answer 3

bss ( Block Started by Symbol ) stores the zero-value initialised static-allocated variables (including global and static variables). If the initialised value of a static-allocated is not 0 , eg:

int global = 5;

Then the global will be allocated in data section.