startup.s для Cortex M4 Опции

[vanek18]

Добрый день! Подскажите пожалуйста, в startup.s для Cortex-M4 в обработчике сброса написано следующее:

CODE

Reset_Handler PROC
EXPORT Reset_Handler [WEAK]
IMPORT __main
IMPORT SystemInit

LDR R0, =SystemInit
BLX R0
LDR R0, =__main
BX R0
ENDP

Почему SystemInit без подчеркивания,а __main с ними...и что вообще значат эти два подчеркивания?

[esaulenka]

Что странно, описание гуглится плохо.

Зато есть локальная копия:

The entry point of a program is at __main in the C library where library code:
- Copies non-root (RO and RW) execution regions from their load addresses to their execution addresses. Also, if any data sections are compressed, they are decompressed from the load address to the execution address.
- Zeroes ZI regions.
- Branches to __rt_entry.

The library function __rt_entry() runs the program as follows:
Sets up the stack and the heap by one of a number of means that include calling __user_setup_stackheap(), calling __rt_stackheap_init(), or loading the absolute addresses of scatter-loaded regions.
Calls __rt_lib_init() to initialize referenced library functions, initialize the locale and, if necessary, set up argc and argv for main().
For C++, calls the constructors for any top-level objects by way of __cpp_initialize__aeabi_.
Calls main(), the user-level root of the application.
From main(), your program might call, among other things, library functions.
Calls exit() with the value returned by main().