User's Manual

Figure 1 High-level View of the Compiler
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:
1. For each source file, the driver calls the language compiler to create an object file. (See also
“What is an Object File?” (page 18))
2. The HP-UX linker (ld) links the specified object files to create either a reusable object file, also
called a shared library, or an executable, which is named a.out by default unless a name
is specified. (See also “Compiler-Linker Interaction” (page 19).)
Figure 2 summarizes how a compiler driver works.
Figure 2 Looking Inside a Compiler
The C, aC++, and Fortran90 compilers provide the -v (verbose) option to display the phases a
compiler is performing.
What is an Object File?
An object file is basically a file containing machine language instructions and data in a form that
the linker can use to create an executable program. Each routine or data item defined in an object
file has a corresponding symbol name by which it is referenced. A symbol generated for a routine
18 Compiling and Linking Programs on HP-UX