Re: hiding xapian symbols

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+Date: Tue, 21 Jun 2011 22:05:15 -0400\r
+From: Daniel Kahn Gillmor <dkg@fifthhorseman.net>\r
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+To: notmuch@notmuchmail.org\r
+Subject: Re: hiding xapian symbols\r
+References: <1308704923-14748-1-git-send-email-david@tethera.net>\r
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+On 06/21/2011 09:08 PM, david@tethera.net wrote:\r
+> Here is my proposal, based on Clint's suggestion on IRC, and on the\r
+> sed hack from librhash, to hide all symbols that are not explicitly\r
+> part of the notmuch API. In particular it hides the various symbols\r
+> related to Xapian exceptions.\r
+\r
+I like this proposal -- i would be really glad to not see the mangled\r
+Xapian symbols in libnotmuch.so.\r
+\r
+However, i'm concerned that the act of hiding these symbols will make it\r
+so that any program that tries to link both libnotmuch and libxapian\r
+will be unable to use these symbols.\r
+\r
+Consider the visiblity rules [0]:\r
+\r
+>> Symbol visibility is "default" by default but if the linker encounters=\r
+=20\r
+>> just one definition with it hidden - just one - that typeinfo symbol=20\r
+>> becomes permanently hidden (remember the C++ standard's ODR - one=20\r
+>> definition rule).=20\r
+\r
+\r
+This makes me think that a program that links against libnotmuch and\r
+libxapian, but actually tries to *use* libxapian's exception handling\r
+may have a problem.\r
+\r
+This is probably best resolved by writing such an executable and seeing\r
+if it behaves, but alas, i haven't done that work.   Any takers?\r
+Perhaps this could be a test in the notmuch test suite?\r
+\r
+       --dkg\r
+\r
+\r
+[0]\r
+http://gcc.gnu.org/wiki/Visibility#Problems_with_C.2B-.2B-_exceptions_.28=\r
+please_read.21.29\r
+\r
+\r
+\r
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