Looking "inside" a Compiler

On the surface, it appears as though an HP-UX compiler generates an a.out file by itself. Actually, an HP-UX compiler is a driver that calls other commands to create the a.out file. The driver performs different tasks (or phases) for different languages, but two phases are common to all languages:

Figure 2-2 “Looking "inside" a Compiler ” summarizes how a compiler driver works.

Figure 2-2 Looking "inside" a Compiler

The C, C++, FORTRAN, and Pascal compilers provide the -v (verbose) option to display the phases a compiler is performing. Compiling main.c and func.c with the -v option produced this output on a Series 700 workstation (\ at the end of a line indicates the line is continued to the next line):

$ cc -Aa -v main.c func.c -lm
cc: CCOPTS is not set.
main.c:
/opt/langtools/lbin/cpp.ansi main.c /var/tmp/ctmAAAa10102 \\
  -D__hp9000s700 -D__hp9000s800 -D__hppa -D__hpux \\
  -D__unix -D_PA_RISC1_1
cc: Entering Preprocessor.
/opt/ansic/lbin/ccom /var/tmp/ctmAAAa10102 main.o -O0 -Aa \\
  func.c:
/opt/langtools/lbin/cpp.ansi func.c /var/tmp/ctmAAAa10102 \\
  -D__hp9000s700 -D__hp9000s800 -D__hppa -D__hpux \\
  -D__unix -D_PA_RISC1_1
cc: Entering Preprocessor.
/opt/ansic/lbin/ccom /var/tmp/ctmAAAa10102 func.o -O0 -Aa
cc: LPATH is /usr/lib/pa1.1:/usr/lib:/opt/langtools/lib:
/usr/ccs/bin/ld /opt/langtools/lib/crt0.o -u main main.o func.o \\
  -lm -lc
cc: Entering Link editor.

This example shows that the cc driver calls the C preprocessor (/opt/langtools/lbin/cpp.ansi) for each source file, then calls the actual C compiler (/opt/ansic/lbin/ccom) to create the object files. Finally, the driver calls the linker (/usr/ccs/bin/ld) on the object files created by the compiler (main.o and func.o).