Memory layout of program

Memory is divided into kernel space and user space . The user memory space is divided into the following areas from low to high ：

Reserves ：

A protected and inaccessible area of memory , In most operating systems, tiny addresses are usually not allowed to be accessed , therefore C The language assigns an invalid pointer to 0.

Code segment ：

Store executable code （ Binary format ）, And constant values （ Like string constants ）, Can be shared by multiple programs , read-only .

Initialization data segment (.data)：

Store initialized global and static variables . This type of data , Will allocate memory space before the program runs .

Uninitialized data segment (.bss)：

Store uninitialized global variables and static variables ..data All the data of the segment has been divided into spaces , however .bss The segment does not give space to the data in it .

This is an all zero memory segment , Initialize to 0 Global and static variables of are also stored here .

Pile up (.heap)：

Store dynamically allocated memory , If you use malloc/calloc/realloc/new Allocated memory . Upward increase . Generally much larger than the stack . Need to free up space manually .

Memory mapping area of shared library ：

Store dynamic library / Static library , And file mapping , Anonymous mapping and other dependent things .

Stack (.stack)：

Store local variables , Parameters and return values of functions , And registers that need to remain unchanged before and after function calls （ Context ）. Grow down . The operating system reclaims space by itself .

Reference resources ：

​ ​https://blog.csdn.net/Code_beeps/article/details/89608929​​

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