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dlltool
may be used to create the files needed to build and use dynamic link libraries (DLLs).
Warning: dlltool
is not always built as part of the binary utilities, since it is only useful for those targets which support DLLs.
dlltool [-d
|--input-def
def-file-name] [-b
|--base-file
base-file-name] [-e
|--output-exp
exports-file-name] [-z
|--output-def
def-file-name] [-l
|--output-lib
library-file-name] [--export-all-symbols
] [--no-export-all-symbols
] [--exclude-symbols
list] [--no-default-excludes
] [-S
|--as
path-to-assembler] [-f
|--as-flags
options] [-D
|--dllname
name] [-m
|--machine
machine] [-a
|--add-indirect
] [-U
|--add-underscore
] [-k
|--kill-at
] [-A
|--add-stdcall-alias
] [-x
|--no-idata4
] [-c
|--no-idata5
] [-i
|--interwork
] [-n
|--nodelete
] [-t
|--temp-prefix
prefix] [-v
|--verbose
] [-h
|--help
] [-V
|--version
] [object-file ...]
dlltool
reads its inputs, which can come from the -d
and -b
options as well as object files specified on the command line. It then processes these inputs and if the -e
option has been specified it creates a exports file. If the -l
option has been specified it creates a library file and if the -z
option has been specified it creates a def file. Any or all of the -e
, -l
and -z
options can be present in one invocation of dlltool.
When creating a DLL, along with the source for the DLL, it is necessary to have three other files. dlltool
can help with the creation of these files.
The first file is a .def
file which specifies which functions are exported from the DLL, which functions the DLL imports, and so on. This is a text file and can be created by hand, or dlltool
can be used to create it using the -z
option. In this case dlltool
will scan the object files specified on its command line looking for those functions which have been specially marked as being exported and put entries for them in the .def file it creates.
In order to mark a function as being exported from a DLL, it needs to have an -export:<name_of_function>
entry in the .drectve
section of the object file. This can be done in C by using the asm() operator:
asm (".section .drectve"); asm (".ascii \"-export:my_func\""); int my_func (void) { ... }
The second file needed for DLL creation is an exports file. This file is linked with the object files that make up the body of the DLL and it handles the interface between the DLL and the outside world. This is a binary file and it can be created by giving the -e
option to dlltool
when it is creating or reading in a .def file.
The third file needed for DLL creation is the library file that programs will link with in order to access the functions in the DLL. This file can be created by giving the -l
option to dlltool when it is creating or reading in a .def file.
dlltool
builds the library file by hand, but it builds the exports file by creating temporary files containing assembler statements and then assembling these. The -S
command line option can be used to specify the path to the assembler that dlltool will use, and the -f
option can be used to pass specific flags to that assembler. The -n
can be used to prevent dlltool from deleting these temporary assembler files when it is done, and if -n
is specified twice then this will prevent dlltool from deleting the temporary object files it used to build the library.
Here is an example of creating a DLL from a source file dll.c
and also creating a program (from an object file called program.o
) that uses that DLL:
gcc -c dll.c dlltool -e exports.o -l dll.lib dll.o gcc dll.o exports.o -o dll.dll gcc program.o dll.lib -o program
The command line options have the following meanings:
-d
filename--input-def
filename-b
filename--base-file
filename-e
filename--output-exp
filename-z
filename--output-def
filename-l
filename--output-lib
filename--export-all-symbols
--no-default-excludes
option. You may add to the list of symbols to not export by using the --exclude-symbols
option.--no-export-all-symbols
.drectve
sections in the input object files. This is the default behaviour. The .drectve
sections are created by dllexport
attributes in the source code.--exclude-symbols
list--export-all-symbols
is used.--no-default-excludes
--export-all-symbols
is used, it will by default avoid exporting certain special symbols. The current list of symbols to avoid exporting is DllMain@12
, DllEntryPoint@0
, impure_ptr
. You may use the --no-default-excludes
option to go ahead and export these special symbols. This is only meaningful when --export-all-symbols
is used.-S
path--as
path-f
options--as-flags
options-S
option is not used. This option only takes one argument, and if it occurs more than once on the command line, then later occurrences will override earlier occurrences. So if it is necessary to pass multiple options to the assembler they should be enclosed in double quotes.-D
name--dll-name
name-e
option is used. If this option is not present, then the filename given to the -e
option will be used as the name of the DLL.-m
machine-machine
machinedlltool
has a built in default type, depending upon how it was created, but this option can be used to override that. This is normally only useful when creating DLLs for an ARM processor, when the contents of the DLL are actually encode using Thumb instructions.-a
--add-indirect
dlltool
is creating the exports file it should add a section which allows the exported functions to be referenced without using the import library. Whatever the hell that means!-U
--add-underscore
dlltool
is creating the exports file it should prepend an underscore to the names of the exported functions.-k
--kill-at
dlltool
is creating the exports file it should not append the string @ <number>
. These numbers are called ordinal numbers and they represent another way of accessing the function in a DLL, other than by name.-A
--add-stdcall-alias
dlltool
is creating the exports file it should add aliases for stdcall symbols without @ <number>
in addition to the symbols with @ <number>
.-x
--no-idata4
dlltool
is creating the exports and library files it should omit the .idata4
section. This is for compatibility with certain operating systems.-c
--no-idata5
dlltool
is creating the exports and library files it should omit the .idata5
section. This is for compatibility with certain operating systems.-i
--interwork
dlltool
should mark the objects in the library file and exports file that it produces as supporting interworking between ARM and Thumb code.-n
--nodelete
dlltool
preserve the temporary assembler files it used to create the exports file. If this option is repeated then dlltool will also preserve the temporary object files it uses to create the library file.-t
prefix--temp-prefix
prefixdlltool
use prefix when constructing the names of temporary assembler and object files. By default, the temp file prefix is generated from the pid.-v
--verbose
-h
--help
-V
--version