main 
   validate_all_switches 
   lookup_compiler 
   do_spec 
      do_spec_2 
         do_spec_1 	/* Get hold of the name of the compiler */
      execute 
         pex_init 
         pex_run 
            pex_run_in_environment 
               obj->funcs->exec_child 



/*********************************** gcc.c ********************************************/
int
main (int argc, char **argv)
{

  validate_all_switches ();

  for (i = 0; (int) i < n_infiles; i++)
    {
      const char *name = infiles[i].name;
      struct compiler *compiler = lookup_compiler (name,
						   strlen (name),
						   infiles[i].language);
      infiles[i].incompiler = compiler;
    }

  for (i = 0; (int) i < n_infiles; i++)
    {
      input_file_compiler = infiles[i].incompiler;

      if (input_file_compiler)
	{
	  /* Ok, we found an applicable compiler.  Run its spec.  */

	      value = do_spec (input_file_compiler->spec);
	      infiles[i].compiled = true;
	    }
	}

    }

  /* Run ld to link all the compiler output files.  */

      value = do_spec (link_command_spec);
}

static struct compiler *
lookup_compiler (const char *name, size_t length, const char *language)
{
  struct compiler *cp;

  return cp;

}

struct compiler
{
  const char *suffix;		/* Use this compiler for input files
				   whose names end in this suffix.  */

  const char *spec;		/* To use this compiler, run this spec.  */

  const char *cpp_spec;         /* If non-NULL, substitute this spec
				   for `%C', rather than the usual
				   cpp_spec.  */
  const int combinable;          /* If nonzero, compiler can deal with
				    multiple source files at once (IMA).  */
  const int needs_preprocessing; /* If nonzero, source files need to
				    be run through a preprocessor.  */
};

/* The default list of file name suffixes and their compilation specs.  */

static const struct compiler default_compilers[] =
{
  {".m",  "#Objective-C", 0, 0, 0}, {".mi",  "#Objective-C", 0, 0, 0},
  {".mm", "#Objective-C++", 0, 0, 0}, {".M", "#Objective-C++", 0, 0, 0},
  {".mii", "#Objective-C++", 0, 0, 0},
  {".cc", "#C++", 0, 0, 0}, {".cxx", "#C++", 0, 0, 0},
  {".cpp", "#C++", 0, 0, 0}, {".cp", "#C++", 0, 0, 0},
  {".c++", "#C++", 0, 0, 0}, {".C", "#C++", 0, 0, 0},
  {".CPP", "#C++", 0, 0, 0}, {".ii", "#C++", 0, 0, 0},
  {".ads", "#Ada", 0, 0, 0}, {".adb", "#Ada", 0, 0, 0},
  {".f", "#Fortran", 0, 0, 0}, {".F", "#Fortran", 0, 0, 0},
  {".for", "#Fortran", 0, 0, 0}, {".FOR", "#Fortran", 0, 0, 0},
  {".ftn", "#Fortran", 0, 0, 0}, {".FTN", "#Fortran", 0, 0, 0},
  {".fpp", "#Fortran", 0, 0, 0}, {".FPP", "#Fortran", 0, 0, 0},
  {".f90", "#Fortran", 0, 0, 0}, {".F90", "#Fortran", 0, 0, 0},
  {".f95", "#Fortran", 0, 0, 0}, {".F95", "#Fortran", 0, 0, 0},
  {".f03", "#Fortran", 0, 0, 0}, {".F03", "#Fortran", 0, 0, 0},
  {".f08", "#Fortran", 0, 0, 0}, {".F08", "#Fortran", 0, 0, 0},
  {".r", "#Ratfor", 0, 0, 0},
  {".p", "#Pascal", 0, 0, 0}, {".pas", "#Pascal", 0, 0, 0},
  {".java", "#Java", 0, 0, 0}, {".class", "#Java", 0, 0, 0},
  {".zip", "#Java", 0, 0, 0}, {".jar", "#Java", 0, 0, 0},
  /* Next come the entries for C.  */
  {".c", "@c", 0, 1, 1},
  {"@c",
   /* cc1 has an integrated ISO C preprocessor.  We should invoke the
      external preprocessor if -save-temps is given.  */
                "...", 0, 1, 1},
  {"-",
   "%{!E:%e-E or -x required when input is from standard input}\
    %(trad_capable_cpp) %(cpp_options) %(cpp_debug_options)", 0, 0, 0},
  {".h", "@c-header", 0, 0, 0},
  {"@c-header",
   /* cc1 has an integrated ISO C preprocessor.  We should invoke the
      external preprocessor if -save-temps is given.  */
     "", 0, 0, 0},
  {".i", "@cpp-output", 0, 1, 0},
  {"@cpp-output",
   "%{!M:%{!MM:%{!E:cc1 -fpreprocessed %i %(cc1_options) %{!fsyntax-only:%(invoke_as)}}}}", 0, 1, 0},
  {".s", "@assembler", 0, 1, 0},
  {"@assembler",
   "%{!M:%{!MM:%{!E:%{!S:as %(asm_debug) %(asm_options) %i %A }}}}", 0, 1, 0},
  {".sx", "@assembler-with-cpp", 0, 1, 0},
  {".S", "@assembler-with-cpp", 0, 1, 0},
  {"@assembler-with-cpp",
#ifdef AS_NEEDS_DASH_FOR_PIPED_INPUT
   "%(trad_capable_cpp) -lang-asm %(cpp_options) -fno-directives-only\
      %{E|M|MM:%(cpp_debug_options)}\
      %{!M:%{!MM:%{!E:%{!S:-o %|.s |\n\
       as %(asm_debug) %(asm_options) %|.s %A }}}}"
#else
   "%(trad_capable_cpp) -lang-asm %(cpp_options) -fno-directives-only\
      %{E|M|MM:%(cpp_debug_options)}\
      %{!M:%{!MM:%{!E:%{!S:-o %|.s |\n\
       as %(asm_debug) %(asm_options) %m.s %A }}}}"
#endif
   , 0, 1, 0},

#include "specs.h"
  /* Mark end of table.  */
  {0, 0, 0, 0, 0}
};

----------------------------------------------------------------------------------------------------------

int
do_spec (const char *spec)
{
  int value;

  value = do_spec_2 (spec);

  value = execute ();

  return value;
}

static int
do_spec_2 (const char *spec)
{

  result = do_spec_1 (spec, 0, NULL);

  return result;
}

static int
do_spec_1 (const char *spec, int inswitch, const char *soft_matched_part)
{
	  {
	    value = execute ();
	    if (value)
	      return value;
	  }
	    /* Here are digits and numbers that just process
	       a certain constant string as a spec.  */

	  case '1':
	    value = do_spec_1 (cc1_spec, 0, NULL);
	    if (value != 0)
	      return value;
	    break;

	  case '2':
	    value = do_spec_1 (cc1plus_spec, 0, NULL);
	    if (value != 0)
	      return value;
	    break;

	  case 'a':
	    value = do_spec_1 (asm_spec, 0, NULL);
	    if (value != 0)
	      return value;
	    break;

	  case 'A':
	    value = do_spec_1 (asm_final_spec, 0, NULL);
	    if (value != 0)
	      return value;
	    break;

	  case 'C':
	    {
	      const char *const spec
		= (input_file_compiler->cpp_spec
		   ? input_file_compiler->cpp_spec
		   : cpp_spec);
	      value = do_spec_1 (spec, 0, NULL);
	      if (value != 0)
		return value;
	    }
	    break;

	  case 'l':
	    value = do_spec_1 (link_spec, 0, NULL);
	    if (value != 0)
	      return value;
	    break;

	  case 'L':
	    value = do_spec_1 (lib_spec, 0, NULL);
	    if (value != 0)
	      return value;
	    break;

	  case 'G':
	    value = do_spec_1 (libgcc_spec, 0, NULL);
	    if (value != 0)
	      return value;
	    break;

  return result;
}

static int
execute (void)
{
  struct command *commands;	/* each command buffer with above info.  */

 
  /* Run each piped subprocess.  */

  pex = pex_init (PEX_USE_PIPES | (report_times ? PEX_RECORD_TIMES : 0),
		  programname, temp_filename);
  for (i = 0; i < n_commands; i++)
    {
      const char *string = commands[i].argv[0];

      errmsg = pex_run (pex,
			((i + 1 == n_commands ? PEX_LAST : 0)
			 | (string == commands[i].prog ? PEX_SEARCH : 0)),
			string, CONST_CAST (char **, commands[i].argv),
			NULL, NULL, &err);
    }

  execution_count++;

  /* Wait for all the subprocesses to finish.  */

    pex_free (pex);

}

/************************************  libiberty/pex-common.c **************************************/

/* Run a program.  */

const char *
pex_run (struct pex_obj *obj, int flags, const char *executable,
       	 char * const * argv, const char *orig_outname, const char *errname,
         int *err)
{
  return pex_run_in_environment (obj, flags, executable, argv, NULL,
				 orig_outname, errname, err);
}

/* As for pex_run (), but permits the environment for the child process
   to be specified. */

const char *
pex_run_in_environment (struct pex_obj *obj, int flags, const char *executable,
       	                char * const * argv, char * const * env,
                        const char *orig_outname, const char *errname,
                  	int *err)
{
  /* Run the program.  */

  pid = obj->funcs->exec_child (obj, flags, executable, argv, env,
				in, out, errdes, toclose, &errmsg, err);
}