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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'] [`-v'|`--verbose']
[`-h'|`--help'] [`-V'|`--version']
[object-file ...]
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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) { ... }
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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-export-all-symbols
--exclude-symbols list
--no-default-excludes
-S path
--as path
-f options
--as-flags options
-D name
--dll-name name
-m machine
-machine machine
dlltool 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.
-v
--verbose
-h
--help
-V
--version
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