gcc specs

The gcc compiler is a driver program. It invokes a sequence of other programs to compile, assemble and link. GCC interprets its command-line parameters and uses these to deduce which programs it should invoke, and which command-line options it ought to place on their command lines. This behavior is controlled by spec strings. In most cases there is one spec string for each program that GCC can invoke, but a few programs have multiple spec strings to control their behavior.

The spec strings built into GCC can be overridden by using the -specs= command-line switch to specify a spec file. 

Spec files are plaintext files that are used to construct spec strings. They consist of a sequence of directives separated by blank lines. The type of directive is determined by the first non-whitespace character on the line and it can be one of the following: 

%command 
e.g.
%rename link                old_link


*[spec_name]: 
create, override or delete the named spec string
e.g. Modify link

*link:
-T redboot.ld%s -Ttext 0x20000 %(old_link)

[suffix]:
when this suffix is encountered, the defined spec will be used
e.g.
.c

gcc -input %i

.cpp
g++ -input %i

GCC has the following spec strings built into it. Spec files can override these strings or create their own. Note that individual targets can also add their own spec strings to this list.

     asm          Options to pass to the assembler
     asm_final    Options to pass to the assembler post-processor
     cpp          Options to pass to the C preprocessor
     cc1          Options to pass to the C compiler
     cc1plus      Options to pass to the C++ compiler
     endfile      Object files to include at the end of the link
     link         Options to pass to the linker
     lib          Libraries to include on the command line to the linker
     libgcc       Decides which GCC support library to pass to the linker
     linker       Sets the name of the linker
     predefines   Defines to be passed to the C preprocessor
     signed_char  Defines to pass to CPP to say whether char is signed
                  by default
     startfile    Object files to include at the start of the link
     

REF: http://gcc.gnu.org/onlinedocs/gcc-3.1/gcc/Spec-Files.html