Version 3 (modified by 12 years ago) ( diff ) | ,
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Exporting Symbols
Some ports limit the exported symbols. We need to mark API symbols as exported when we use it outside the library. Since WebKit consists of a set of libraries (WTF, JavaScriptCore, WebCore, WebKit), each library need to export symbols if the API is used from a different library.
There is two primary way to export symbols: export lists and inline annotations. Some ports use export lists. others use inline annotations, or even both.
Export Lists
An export list is a text file which contains the list of exporting symbols. Linkers refer these files to decide which symbols should be exported.
Ports have their own separate lists:
- trunk/Source/WebCore/WebCore.exp.in
- Mac port uses this to build WebCore.framework.
- trunk/Source/JavaScriptCore/JavaScriptCore.vcproj/JavaScriptCore/JavaScriptCore.def
- Win ports use this to build JavaScriptCore.dll
- trunk/Source/autotools/symbols.filter
- GTK port uses this to build libwebkitgtk.so
- trunk/Source/WebKit2/mac/WebKit2.order
- Mac WebKi2 port uses this to build WebKit2.framework
- trunk/Source/WebKit2/win/WebKit2.def.in
- Apple Win and CFLite Win ports use this to build WebKit2.dll
Inline Annotations
Inline annotations is compiler-specific qualifiers which are encapsulated by a set of macros. These macros are defined in following files:
- Source/JavaScriptCore/wtf/ExportMacros.h
- WTF_EXPORT_PRIVATE
- Source/JavaScriptCore/runtime/JSExportMacros.h
- JS_EXPORT_PRIVATE, JS_EXPORTDATA
- Source/WebCore/platform/PlatformExportMacros.h
- (TODO: List port specific definitions for WebKit API layer here.)
Inline annotations are adopted as following:
- Mac port uses WTF_EXPORT, WTF_EXPORT_PRIVATE, JS_EXPORT, JS_EXPORT_PRIVATE, JS_EXPORTDATA to export WTF and JSC symbols.
- Win ports use it JS_EXPORTDATA for exporting JSC static variables.
- Many port have use their own inline annotations to export their WebKit API.
Caveat
- You cannot export inline function.
- If you need to export C++ vtables (that rarely happens though), you need to add JS_EXPORT_PRIVATE or WTF_EXPORT_PRIVATE to the class definition.
How can I export my symbols?
Here are some typical scenarios when you need to care about symbol export:
Exporting WebCore symbols to use them from port WebKit implementations
- If you use it from Mac(WK1), you need to edit WebCore.exp.in.
- Otherwise you don't need to do anything about symbols.
Exporting JavaScriptCore/WTF symbols to use them from port WebCore
- You need to edit JavaScriptCore.def
- You need to add JS_EXPORT_PRIVATE or WTF_EXPORT_PRIVATE to the function.
Exporting WebCore symbols to use them from Internals object (WebCoreTestSupport)
- Only WebCore symbols need to be exported which are used in Internals (if not already exported. Check previous definitions first)
- Internals symbols need not be exported.
For WTF/JavaScriptCore symbols,
- You need to edit JavaScriptCore.def.
- You also need to add JS_EXPORT_PRIVATE or WTF_EXPORT_PRIVATE to exporting functions.
For WebCore symbols, you need to edit following files...
- WebCore.exp.in, symbols.filter, WebKit2.order, WebKit2.def, WebKit2CFLite.def
Exporting WTF/JavaScriptCore/WebCore symbols to use them from DumpRenderTree
- You shouldn't do it.
- If you inevitably need to do it, it's same as the Internals appraoch noted above.
Exporting WebKit API symbols to applications
TODO: Write port specific way to do this.