@node __crt0_glob_function, startup
@subheading Syntax

@example
#include <crt0.h>

char **__crt0_glob_function(char *_argument);
@end example

@subheading Description

If the application wishes to provide a wildcard expansion function, it
should define a @code{__crt0_glob_function} function.  It should return
a list of the expanded values, or 0 if no expansion will occur.  The
startup code will free the returned pointer if it is nonzero.

If no expander function is provided, wildcards will be expanded in the
POSIX.1 style by the default @code{__crt0_glob_function} from the C
library.  To disable expansion, provide a @code{__crt0_glob_function}
that always returns 0.

@subheading Portability

@portability !ansi, !posix

@c ----------------------------------------------------------------------
@node __crt0_setup_arguments, startup
@subheading Syntax

@example
#include <crt0.h>

void   __crt0_setup_arguments(void);
@end example

@subheading Description

This function, provided by libc.a, does all the work required to
provide the two arguments passed to main() (usually @code{argc} and
@code{argv}).  If main() does not use these arguments, the programmer
can reduce the size of the program image by providing a version of
this function that does nothing.

Note that since the default @code{__crt0_setup_arguments_function} will
@emph{not} expand wildcards inside quotes (@kbd{"} or @kbd{'}), you
can quote a part of the argument that doesn't include wildcards and
still have them expanded.  This is so you could use wildcard expansion
with filenames which have embedded whitespace (on LFN filesystems).

@xref{__crt0_load_environment_file}.

@subheading Portability

@portability !ansi, !posix

@c ----------------------------------------------------------------------
@node __crt0_load_environment_file, startup
@subheading Syntax

@example
#include <crt0.h>

void   __crt0_load_environment_file(char *_app_name);
@end example

@subheading Description

This function, provided by libc.a, does all the work required to load
additional environment variables from the file @file{djgpp.env} whose
full pathname is given by the @code{DJGPP} environment variable.  If the
application does not use environment variables, the programmer can
reduce the size of the program image by providing a version of this
function that does nothing.

@xref{__crt0_setup_arguments}.

@subheading Portability

@portability !ansi, !posix

@c ----------------------------------------------------------------------
@node _crt0_startup_flags, startup
@subheading Syntax

@example
#include <crt0.h>

int _crt0_startup_flags = ...;
@end example

@subheading Description

This variable can be used to determine what the startup code will (or
will not) do when the program begins.  This can be used to tailor the
startup environment to a particular program.

@table @code

@item _CRT0_FLAG_PRESERVE_UPPER_CASE

If set, @code{argv[0]} is left in whatever case it was.  If not set, all
characters are mapped to lower case.  Note that if the @code{argv0}
field in the @dfn{stubinfo} structure is present, the case of that part
of @code{argv[0]} is not affected. 

@item _CRT0_FLAG_USE_DOS_SLASHES

If set, reverse slashes (dos-style) are preserved in @code{argv[0]}.  If
not set, all reverse slashes are replaced with unix-style slashes.

@item _CRT0_FLAG_DROP_EXE_SUFFIX

If set, the @file{.exe} suffix is removed from the file name component
of @code{argv[0]}.  If not set, the suffix remains. 

@item _CRT0_FLAG_DROP_DRIVE_SPECIFIER

If set, the drive specifier (e.g. @file{C:}) is removed from the
beginning of @code{argv[0]} (if present).  If not set, the drive
specifier remains.

@item _CRT0_FLAG_DISALLOW_RESPONSE_FILES

If set, response files (e.g. @file{@@gcc.rf}) are not expanded.  If not
set, the contents of the response files are used to create arguments.
Note that if the file does not exist, that argument remains unexpanded. 

@item _CRT0_FLAG_KEEP_QUOTES

If set, the quote characters @samp{'}, @samp{"}, and @samp{\} will be
retained in @code{argv[]} elements when processing command lines passed
by DOS and via @code{system}.  This is used by the @code{redir} program,
and should only be needed if you want to get the original command line
exactly as it was passed by the caller.

@item _CRT0_FLAG_FILL_SBRK_MEMORY

If set, fill @code{sbrk}'d memory with a constant value.  If not, memory
gets whatever happens to have been in there, which breaks some
applications.

@item _CRT0_FLAG_FILL_DEADBEEF

If set, fill memory (above) with @code{0xdeadbeef}, else fill with zero.
This is especially useful for debugging uninitialized memory problems.

@item _CRT0_FLAG_NEARPTR

If set, set DS limit to 4GB which allows use of near pointers to DOS
(and other) memory.  WARNING, disables memory protection and bad
pointers may crash the machine or wipe out your data.  This flag is
silently ignored on NT and DOSEmu, which disallow such huge selector
limits.

@item _CRT0_FLAG_NULLOK

If set, disable @sc{null} pointer protection (if it can be controlled at
all).

@item _CRT0_FLAG_NMI_SIGNAL

If set, enabled capture of NMI in exception code.  This may cause problems
with laptops and "green" boxes which use it to wake up.  Default is to 
leave NMIs alone and pass through to real mode code.  You decide.

@item _CRT0_FLAG_NO_LFN

If set, disable usage of long file name functions even on systems (such
as Windows 9X) which support them.  This might be needed to work around
program assumptions on file name format on programs written specifically
for DOS.  Note that this flag overrides the value of the environment
variable @code{LFN}.

@item _CRT0_FLAG_NONMOVE_SBRK

If set, the @code{sbrk} algorithm uses multiple DPMI memory blocks which
makes sure the base of CS/DS/SS does not change.  This may cause
problems with @code{sbrk(0)} values and programs with other assumptions
about @code{sbrk} behavior.  This flag is useful with near pointers,
since a constant pointer to DOS/Video memory can be computed without
needing to reload it after any routine which might call @code{sbrk}.

@item _CRT0_FLAG_UNIX_SBRK

If set, the @code{sbrk} algorithm resizes memory blocks so that the
layout of memory is set up to be the most compatible with Unix
@code{sbrk} expectations.  This mode should not be used with hardware
interrupts, near pointers, and may cause problems with QDPMI virtual
memory.  On NT, this is the recommended algorithm.

If your program requires a specific @code{sbrk} behavior, you
should set either this or the previous flag, since the default may
change in different libc releases.

@item _CRT0_FLAG_LOCK_MEMORY

If set, locks all memory as it is allocated.  This effectively disables
virtual memory, and may be useful if using extensive hardware interrupt
codes in a relatively small image size.  The memory is locked after it
is @code{sbrk}'ed, so the locking may fail.  This bit may be set or cleared
during execution.  When @code{sbrk} uses multiple memory zones, it can be
difficult to lock all memory since the memory block size and location is
impossible to determine.

@item _CRT0_FLAG_PRESERVE_FILENAME_CASE

If set, disables all filename letter-case conversions in functions that
traverse directories (except findfirst/findnext which always return the
filenames exactly as found in the directory entry).  When reset, all
filenames on 8+3 MSDOS filesystems and DOS-style 8+3 filenames on LFN
systems are converted to lower-case by functions such as `readdir',
@code{getcwd}, @code{_fixpath} and others.  Note that when this flag is
set, ALL filenames on MSDOS systems will appear in upper-case, which is
both ugly and will break many Unix-born programs.  Use only if you know
exactly what you are doing!

This flag overrides the value of the environment variable @samp{FNCASE},
@xref{_preserve_fncase}.

@end table

@subheading Portability

@portability !ansi, !posix