dyld-97.1.tar.gz

[apple/dyld.git] / doc / man / man1 / dyld.1

.TH DYLD 1 "March 23, 2007" "Apple Inc."
.SH NAME
dyld \- the dynamic link editor
.SH SYNOPSIS
DYLD_FRAMEWORK_PATH
.br
DYLD_FALLBACK_FRAMEWORK_PATH
.br
DYLD_LIBRARY_PATH
.br
DYLD_FALLBACK_LIBRARY_PATH
.br
DYLD_ROOT_PATH
.br
DYLD_SHARED_REGION
.br
DYLD_INSERT_LIBRARIES
.br
DYLD_FORCE_FLAT_NAMESPACE
.br
DYLD_IMAGE_SUFFIX
.br
DYLD_PRINT_OPTS
.br
DYLD_PRINT_ENV
.br
DYLD_PRINT_LIBRARIES
.br
DYLD_PRINT_LIBRARIES_POST_LAUNCH
.br
DYLD_BIND_AT_LAUNCH
.br
DYLD_NO_FIX_PREBINDING
.br
DYLD_DISABLE_DOFS
.br
DYLD_PRINT_APIS
.br
DYLD_PRINT_BINDINGS
.br
DYLD_PRINT_INITIALIZERS
.br
DYLD_PRINT_REBASINGS
.br
DYLD_PRINT_SEGMENTS
.br
DYLD_PRINT_STATISTICS
.br
DYLD_PRINT_DOFS
.SH DESCRIPTION
The dynamic linker uses the following environment variables.
They affect any program that uses the dynamic linker.
.TP
.B DYLD_FRAMEWORK_PATH
This is a colon separated list of directories that contain frameworks.
The dynamic linker searches these directories before it searches for the
framework by its install name.
It allows you to test new versions of existing
frameworks. (A framework is a library install name that ends in the form
XXX.framework/Versions/YYY/XXX or XXX.framework/XXX, where XXX and YYY are any
name.)
.IP
For each framework that a program uses, the dynamic linker looks for the
framework in each directory in 
.SM DYLD_FRAMEWORK_PATH
in turn. If it looks in all the directories and can't find the framework, it
searches the directories in  
.SM DYLD_LIBRARY_PATH
in turn. If it still can't find the framework, it then searches 
.SM DYLD_FALLBACK_FRAMEWORK_PATH
and
.SM DYLD_FALLBACK_LIBRARY_PATH
in turn.
.IP
Use the
.B \-L
option to 
.IR otool (1).
to discover the frameworks and shared libraries that the executable
is linked against.
.TP
.B DYLD_FALLBACK_FRAMEWORK_PATH
This is a colon separated list of directories that contain frameworks.
It is used as the default location for frameworks not found in their install
path.

By default, it is set to
/Library/Frameworks:/Network/Library/Frameworks:/System/Library/Frameworks
.TP
.B DYLD_LIBRARY_PATH
This is a colon separated list of directories that contain libraries. The
dynamic linker searches these directories before it searches the default
locations for libraries. It allows you to test new versions of existing
libraries. 
.IP
For each library that a program uses, the dynamic linker looks for it in each
directory in 
.SM DYLD_LIBRARY_PATH
in turn. If it still can't find the library, it then searches 
.SM DYLD_FALLBACK_FRAMEWORK_PATH
and
.SM DYLD_FALLBACK_LIBRARY_PATH
in turn.
.IP
Use the
.B \-L
option to 
.IR otool (1).
to discover the frameworks and shared libraries that the executable
is linked against.
.TP
.B DYLD_FALLBACK_LIBRARY_PATH
This is a colon separated list of directories that contain libraries.
It is used as the default location for libraries not found in their install
path.
By default, it is set
to $(HOME)/lib:/usr/local/lib:/lib:/usr/lib.
.TP
.B DYLD_ROOT_PATH
This is a colon separated list of directories.  The dynamic linker will prepend each of
this directory paths to every image access until a file is found.    
.TP
.B DYLD_SHARED_REGION 
This can be "use" (the default), "avoid", or "private".  Settting it to 
"avoid" tells dyld to not use the shared cache.  All OS dylibs are loaded 
dynamically just like every other dylib.  Setting it to "private" tells
dyld to remove the shared region from the process address space and mmap()
back in a private copy of the dyld shared cache in the shared region address
range. This is only useful if the shared cache on disk has been updated 
and is different than the shared cache in use.
.TP
.B DYLD_INSERT_LIBRARIES
This is a colon separated list of dynamic libraries to load before the ones
specified in the program.  This lets you test new modules of existing dynamic
shared libraries that are used in flat-namespace images by loading a temporary
dynamic shared library with just the new modules.  Note that this has no
effect on images built a two-level namespace images using a dynamic shared
library unless
.SM DYLD_FORCE_FLAT_NAMESPACE
is also used.
.TP
.B DYLD_FORCE_FLAT_NAMESPACE
Force all images in the program to be linked as flat-namespace images and ignore
any two-level namespace bindings.  This may cause programs to fail to execute
with a multiply defined symbol error if two-level namespace images are used to
allow the images to have multiply defined symbols.
.TP
.B DYLD_IMAGE_SUFFIX
This is set to a string of a suffix to try to be used for all shared libraries
used by the program.  For libraries ending in ".dylib" the suffix is applied
just before the ".dylib".  For all other libraries the suffix is appended to the
library name.  This is useful for using conventional "_profile" and "_debug"
libraries and frameworks.
.TP
.B DYLD_PRINT_OPTS
When this is set, the dynamic linker writes to file descriptor 2 (normally
standard error) the command line options.
.TP
.B DYLD_PRINT_ENV
When this is set, the dynamic linker writes to file descriptor 2 (normally
standard error) the environment variables.
.TP
.B DYLD_PRINT_LIBRARIES
When this is set, the dynamic linker writes to file descriptor 2 (normally
standard error) the filenames of the libraries the program is using.
This is useful to make sure that the use of
.SM DYLD_LIBRARY_PATH
is getting what you want.
.TP
.B DYLD_PRINT_LIBRARIES_POST_LAUNCH
This does the same as
.SM DYLD_PRINT_LIBRARIES
but the printing starts after the program gets to its entry point.
.TP
.B DYLD_BIND_AT_LAUNCH
When this is set, the dynamic linker binds all undefined symbols
the program needs at launch time. This includes function symbols that can are normally 
lazily bound at the time of their first call.
.TP
.B DYLD_PRINT_STATISTICS
Right before the process's main() is called, dyld prints out information about how
dyld spent its time.  Useful for analyzing launch performance.
.TP
.B DYLD_NO_FIX_PREBINDING
Normally, dyld will trigger the dyld shared cache to be regenerated if it notices
the cache is out of date while launching a process.  If this environment variable
is set, dyld will not trigger a cache rebuild.  This is useful to set while installing
a large set of OS dylibs, to ensure the cache is not regenerated until the install
is complete.
.TP
.B DYLD_DISABLE_DOFS 
Causes dyld not register dtrace static probes with the kernel.
.TP
.B DYLD_PRINT_INITIALIZERS
Causes dyld to print out a line when running each initializers in every image.  Initializers
run by dyld included constructors for C++ statically allocated objects, functions marked with
__attribute__((constructor)), and -init functions.
.TP
.B DYLD_PRINT_APIS
Causes dyld to print a line whenever a dyld API is called (e.g. NSAddImage()).
.TP
.B DYLD_PRINT_SEGMENTS
Causes dyld to print out a line containing the name and address range of each mach-o segment
that dyld maps.  In addition it prints information about if the image was from the dyld 
shared cache.
.TP
.B DYLD_PRINT_BINDINGS 
Causes dyld to print a line each time a symbolic name is bound.  
.TP
.B DYLD_PRINT_DOFS 
Causes dyld to print out information about dtrace static probes registered with the kernel. 

.SH "SEE ALSO"
libtool(1), ld(1), otool(1)