What is flag_function_sections in gcc sources?

Question

GCC

I'm trying to compile gcc-4.2 sources (or rather llvm-gcc-4.2). However, I am getting an error:

../../llvm-gcc-4.2-2.9/gcc/toplev.c: In function ‘process_options’:
../../llvm-gcc-4.2-2.9/gcc/toplev.c:1995:11: error: ‘flag_function_sections’ undeclared (first use in this function)
../../llvm-gcc-4.2-2.9/gcc/toplev.c:1995:11: note: each undeclared identifier is reported only once for each function it appears in

What kind of variable is this and where should it be declared (there are also flag_data_sections nearby)?
When I made the announcement:

int flag_function_sections = 0;
  int flag_data_sections = 0;

the error went away, but got out in another file (I feel there are many such places). So what is this variable and how to correctly declare it?

Answer 1

gcc 4.7.0The definition is not found in the source flag_function_sections, it appears in the file gcc/common.opt:

ffunction-sections
Common Report Var(flag_function_sections)
Place each function into its own section

File description:

Options for the language- and target-independent parts of the compiler

Found some old toplev.c file . There is something

/* Nonzero means place each function into its own section on those platforms
   which support arbitrary section names and unlimited numbers of sections.  */

int flag_function_sections = 0;

/* ... and similar for data.  */

int flag_data_sections = 0;