Why do we need both - export maps AND -fvisibility=hidden/__attribute__((visibility("default")))

Magnus Ihse Bursie magnus.ihse.bursie at oracle.com
Wed Feb 12 23:26:46 PST 2014

On 2014-02-05 19:09, Volker Simonis wrote:
> If there are any more/other comments on this topic I'll be highly interested.

You can count on me having lots of opinion on build issues. ;-)

I'd like to get rid of the hard-coded map files completely, both in 
hotspot and jdk. This can be done without loss of functionality. How? 
Because we can generate them on the fly at build time, using information 
provided by the source code.

Note that the exported functions are prefixed by the macro JNIEXPORT. We 
can locate all functions that have this prefix and write them to a map 
file. This can be done, and was indeed the way we solved things back in 
the JRockit JVM. The technique we used there was to grep for "JNIEXPORT" 
and check for a symbol name (as provided by nm). We had rules requiring 
that JNIEXPORT was to be written on the same line as the function name, 
or the line before that. So we could do like "grep -A 1 -e JNIEXPORT" 
and then cross-reference for names extracted by nm. Not exactly a formal 
semantic parsing, but it was efficient and worked very well. I believe 
we can do something very similar for hotspot and jdk.

Then again, if we could get rid of maps completely, by using visibility 
and not linking statically with the standard libs, that would be even 
better. :-)


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