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7.4.8.19 Using gnatdll ¶

gnatdll is a tool to automate the DLL build process once all the Ada and non-Ada sources that make up your DLL have been compiled. gnatdll is actually in charge of two distinct tasks: building both the static import library for the DLL and the actual DLL. You invoke the gnatdll command as

$ gnatdll [ switches ] list-of-files [ -largs opts ]

where list-of-files is a list of ALI and object files. The object file list must be the exact list of objects corresponding to the non-Ada sources whose services are to be included in the DLL. The ALI file list must be the exact list of ALI files for the corresponding Ada sources whose services are to be included in the DLL. If list-of-files is missing, only the static import library is generated.

You may specify any of the following switches to gnatdll:

-a[`address']

Build a non-relocatable DLL at address. If you don’t specify address, gnatdll uses the default address of 0x11000000. By default, when this switch is missing, gnatdll builds a relocatable DLL. We advise you to build relocatable DLL.

-bargs `opts'

Binder switches. Pass opts to the binder.

-d `dllfile'

dllfile is the name of the DLL. You must specify this switch for gnatdll to do anything. gnatdll names the generated import library algorithmically from dllfile as shown in the following example: if dllfile is xyz.dll, the import library name is libxyz.dll.a. gnatdll obtains the name of the definition file (if not specified by switch -e) algorithmically from dllfile as shown in the following example: if dllfile is xyz.dll, the definition file used is xyz.def.

-e `deffile'

deffile is the name of the definition file.

-g

Generate debugging information. This information is stored in the object file and copied from there to the final DLL file by the linker, where it can be read by the debugger. You must use the -g switch if you plan on using the debugger or the symbolic stack traceback.

-h

Help mode. Displays gnatdll switch usage information.

-I`dir'

Direct gnatdll to search the dir directory for source and object files needed to build the DLL. (Search Paths and the Run-Time Library (RTL)).

-k

Removes the @nn suffix from the import library’s exported names, but keeps them for the link names. You must specify this switch if you want to use a Stdcall function in a DLL for which the @nn suffix has been removed. This is the case for most of the Windows NT DLL for example. This switch has no effect if you specify the -n switch.

-l `file'

The list of ALI and object files used to build the DLL are listed in file, instead of being given in the command line. Each line in file contains the name of an ALI or object file.

-n

No Import. Do not create the import library.

-q

Quiet mode. Do not display unnecessary messages.

-v

Verbose mode. Display extra information.

-largs `opts'

Linker switches. Pass opts to the linker.

gnatdll Example ¶

As an example, the command to build a relocatable DLL from api.adb once api.adb has been compiled and api.def created is

$ gnatdll -d api.dll api.ali

The above command creates two files: libapi.dll.a (the import library) and api.dll (the actual DLL). If you want to create only the DLL, just type:

$ gnatdll -d api.dll -n api.ali

Alternatively, if you want to create just the import library, type:

$ gnatdll -d api.dll

gnatdll behind the Scenes ¶

This section details the steps involved in creating a DLL. gnatdll does these steps for you. Unless you are interested in understanding what goes on behind the scenes, you should skip this section.

We use the previous example of a DLL containing the Ada package API, to illustrate the steps necessary to build a DLL. The starting point is a set of objects that make up the DLL and the corresponding ALI files. In the case of this example, this means api.o and api.ali. To build a relocatable DLL, gnatdll does the following:

• builds the base file (api.base). A base file gives the information necessary to generate relocation information for the DLL.

  $ gnatbind -n api
  $ gnatlink api -o api.jnk -mdll -Wl,--base-file,api.base
  

  In addition to the base file, the gnatlink command generates an output file api.jnk, which can be discarded. The -mdll switch asks gnatlink to generate the routines DllMain and DllMainCRTStartup that are called by the Windows loader when the DLL is loaded into memory.

• uses dlltool (see Using dlltool) to build the export table (api.exp). The export table contains the relocation information in a form which can be used during the final link to ensure that the Windows loader is able to place the DLL anywhere in memory.

  $ dlltool --dllname api.dll --def api.def --base-file api.base \\
            --output-exp api.exp
  

• builds the base file using the new export table. Note that gnatbind must be called once again since the binder generated file has been deleted during the previous call to gnatlink.

  $ gnatbind -n api
  $ gnatlink api -o api.jnk api.exp -mdll
        -Wl,--base-file,api.base
  

• builds the new export table using the new base file and generates the DLL import library libAPI.dll.a.

  $ dlltool --dllname api.dll --def api.def --base-file api.base \\
            --output-exp api.exp --output-lib libAPI.a
  

• Finally, builds the relocatable DLL using the final export table.

  $ gnatbind -n api
  $ gnatlink api api.exp -o api.dll -mdll
  

Using dlltool ¶

dlltool is the low-level tool used by gnatdll to build DLLs and static import libraries. This section summarizes the most common dlltool switches. You run dlltool as follows:

$ dlltool [`switches`]

dlltool switches include:

--base-file `basefile'

Read the base file basefile generated by the linker. You use this switch to create a relocatable DLL.

--def `deffile'

Read the definition file.

--dllname `name'

Gives the name of the DLL. You use this switch to embed the name of the DLL in the static import library generated by dlltool with switch --output-lib.

-k

Kill @nn from exported names (Windows Calling Conventions for a discussion about Stdcall-style symbols).

--help

Prints the dlltool switches with a concise description.

--output-exp `exportfile'

Generate an export file exportfile. The export file contains the export table (list of symbols in the DLL) and is used to create the DLL.

--output-lib `libfile'

Generate a static import library libfile.

-v

Verbose mode.

--as `assembler-name'

Use assembler-name as the assembler. The default is as.