HPUX crt0.o[3]
crt0(3) crt0(3)
NAME
crt0.o, gcrt0.o, mcrt0.o, frt0.o, gfrt0.o, mfrt0.o - execution startup
routines
DESCRIPTION
The C and Pascal compilers link in files crt0.o, gcrt0.o, or mcrt0.o
to provide startup capabilities and environment for program execution.
All are identical except that gcrt0.o and mcrt0.o provide additional
functionality for gprof(1) and prof(1) profiling support respectively.
Similarly, the FORTRAN compiler links in either frt0.o, gfrt0.o, or
mfrt0.o.
The following symbols are defined in these routines:
__argc_value A variable of type int containing the number
of arguments.
__argv_value An array of character pointers to the
arguments themselves.
_environ An array of character pointers to the
environment in which the program will run.
This array is terminated by a null pointer.
_SYSTEM_ID A variable of type int containing the system
id value for an executable program.
DEPENDENCIES
Series 300/400
The symbols above are shown as they are visible from C. To access
them from assembly language, add an additional underscore to the
beginning of the symbol. For example, an assembly language program
refers to __argc_value as ___argc_value.
Series 300/400 startup files also define the following symbols which
are listed as when used from assembly language. The state of these
variables can be determined from C by using other library routines
(see is_hw_present(3C)).
flag_68010 A variable of type short. Non-zero if the
processor is a 68010; zero if not.
float_soft A variable of type short. Zero if the
HP98635 floating-point card is present; non-
zero if it is not present.
float_loc A constant defining the location in memory of
the HP98635 floating-point card.
flag_68881 A variable of type short. Non-zero if the
HP68881 floating-point coprocessor is
Hewlett-Packard Company - 1 - HP-UX Release 9.0: August 1992
crt0(3) crt0(3)
present; zero if it is not present.
flag_fpa A variable of type short. Non-zero if the
HP98248 floating-point card is present; zero
if it is not present.
fpa_loc A constant defining the location in memory of
the HP98248 floating-point card.
Series 700/800
All compilers on Series 700 and 800 use the crt0.o, gcrt0.o, or
mcrt0.o file; the files frt0.o, gfrt0.o, and mfrt0.o do not exist.
The Series 700 and 800 start-up files also define the following
additional symbols:
$START$ Execution start address.
_start A secondary startup routine for C programs,
called from $START$, which in turn calls
main. This routine is contained in the C
library rather than the crt0.o file. For
Pascal and FORTRAN programs, this symbol
labels the beginning of the outer block (main
program) and is generated by the compilers.
$global$ The initial address of the program's data
pointer. The startup code loads this address
into general register 27.
$UNWIND_START The beginning of the stack unwind table.
$UNWIND_END The end of the stack unwind table.
$RECOVER_START The beginning of the try/recover table.
$RECOVER_END The end of the try/recover table.
The crt0.o file defines a null procedure for _mcount, so programs
compiled with profiling can be linked without profiling.
The linker defines the following two symbols:
__text_start The beginning address of the program's text
area.
__data_start The beginning address of the program's data
area.
AUTHOR
The features described in this entry originated from AT&T UNIX System
III.
Hewlett-Packard Company - 2 - HP-UX Release 9.0: August 1992
crt0(3) crt0(3)
SEE ALSO
cc(1), f77(1), ld(1), pc(1), prof(1), gprof(1), pc(1), profil(2),
exec(2), is_hw_present(3C), monitor(3C).
Hewlett-Packard Company - 3 - HP-UX Release 9.0: August 1992