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What is ffreestanding in gcc ? What is it used for ? I came across the following :
gcc -ffreestanding -m32 -c kernel.c -o kernel.o and do not understand, what does it mean exactly.
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When you invoke GCC, it normally does preprocessing, compilation, assembly and linking. The "overall options" allow you to stop this process at an intermediate stage. For example, the -c option says not to run the linker.
clause. Compilers options (− x on Linux, and /Qx on Microsoft Windows) control which instructions the compiler uses within a function, while the processor(…) clause controls creation of non-standard functions using wider registers (YMM or ZMM) for passing SIMD data for parameters and results. The processor(…)
-c will instruct gcc to only compile the source file to an .o (object) file but does not invoke the linker. With a project containing many . c files one will typically compile first all . c files to .o files and then link everything together with the libraries.
The g++ Compiler Without this option, g++ creates an executable file. With this option, it creates an object file. If no output file name is given (by option -o), the object file name for file prog.
A freestanding environment is one in which the standard library may not exist, and program startup may not necessarily be at "main". The option -ffreestanding directs the compiler to not assume that standard functions have their usual definition.
By default, GCC will act as the compiler for a hosted implementation, defining __STDC_HOSTED__ as 1 and presuming that when the names of ISO C functions are used, they have the semantics defined in the standard. To make it act as a conforming freestanding implementation for a freestanding environment, use the option -ffreestanding. It will then define __STDC_HOSTED__ to 0, and not make assumptions about the meanings of function names from the standard library.
For more Info, This link may help.
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