Second Stage Initialization Files - 2025.2 English - UG1400

It is a requirement to initialize all global and static variables to 0 according to C standard specification.

• Initialization all global and static variables is a common requirement of all CRTs above.
• The separate routine _crtinit initializes memory in the .bss section of the program. The _crtinit routine is also the wrapper that invokes the main procedure.
• Before invoking the main procedure, it can invoke other initialization functions. The _crtinit routine is supplied by the startup files described below.

crtinit.o

This default, second stage, C startup file performs the following steps:

1. Clears the .bss section to zero.
2. Invokes _program_init.
3. Invokes “constructor” functions (_init).
4. Sets up the arguments for main and invokes main.
5. Invokes “destructor” functions (_fini).
6. Invokes _program_clean and returns.

pgcrtinit.o

The profiling process uses the second stage startup file. This file performs the following steps:

1. Clears the .bss section to zero.
2. Invokes _program_init.
3. Invokes _profile_init to initialize the profiling library.
4. Invokes “constructor” functions (_init).
5. Sets up the arguments for main and invokes main.
6. Invokes “destructor” functions (_fini).
7. Invokes _profile_clean to cleanup the profiling library.
8. Invokes _program_clean, and then returns.

sim-crtinit.o

When the compiler uses the -mno-clearbss switch, it uses this second-stage startup file. This file performs the following steps:

1. Invokes _program_init.
2. Invokes “constructor” functions (_init).
3. Sets up the arguments for main and invokes main.
4. Invokes “destructor” functions (_fini).
5. Invokes _program_clean, and then returns.

sim-pgcrtinit.o

During profiling with the -mno-clearbss switch, this second-stage startup file performs the following steps in order:

1. Invokes _program_init.
2. Invokes _profile_init to initialize the profiling library.
3. Invokes “constructor” functions (_init).
4. Sets up the arguments for and invokes main.
5. Invokes “destructor” functions (_fini).
6. Invokes _profile_clean to cleanup the profiling library.
7. Invokes _program_clean, and then returns.