<br><br><div class="gmail_quote">On Thu, Aug 5, 2010 at 11:53 AM, Matthew Knepley <span dir="ltr"><<a href="mailto:knepley@gmail.com">knepley@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<div class="im">On Thu, Aug 5, 2010 at 11:47 AM, Dmitry Karpeev <span dir="ltr"><<a href="mailto:karpeev@mcs.anl.gov" target="_blank">karpeev@mcs.anl.gov</a>></span> wrote:<br></div><div class="gmail_quote"><div class="im">
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<div>On Thu, Aug 5, 2010 at 11:42 AM, Matthew Knepley <span dir="ltr"><<a href="mailto:knepley@gmail.com" target="_blank">knepley@gmail.com</a>></span> wrote:<br></div><div class="gmail_quote"><div>
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<div><div></div><div>On Thu, Aug 5, 2010 at 11:40 AM, Dmitry Karpeev <span dir="ltr"><<a href="mailto:karpeev@mcs.anl.gov" target="_blank">karpeev@mcs.anl.gov</a>></span> wrote:<br></div></div><div class="gmail_quote">
<div><div></div><div><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
What is the intended behavior of PetscDLSym when called on an empty handle: PetscDLSym(handle=PETSC_NULL, symbol, &value)<br>My understanding was that this should look for symbol in the symbol table of the main executable.<br>
This is based on what happens in the Windows case (#ifdef PETSC_HAVE_WINDOWS_H), <br>but when using dlopen (#ifdef PETSC_HAVE_DLFCN_H), this probably won't behave correctly,as currently implemented. <br>This is because the above call will boil down to <br>
value = dlsym((dlhandle_t)0, symbol), <br>which on many systems returns NULL (e.g., on Ubuntu 9.10).<br>There is a relatively easy fix, which is to obtain the handle of the main executable with, for example,<br> dlhandle = dlopen(0,RTLD_LOCAL|RTLD_LAZY)<br>
followed by<br> value = dlsym(dlhandle,symbol)<br><br>I have played around with it on my box, and it appears to work.<br>I can push that fix, if that's what we decide we want, and if it doesn't alter the currently expected behavior.<br>
There is one caveat: symbols can be dlsym'ed from the executable only if they are exported as dynamically-loadable,<br>which is not the default behavior for linking executable (so as not to pollute the dynamic symbol table).<br>
On linux the linker needs to get -Wl,--export-dynamic, but it would be nice to enable some sort of portable option at compile time.<br></blockquote><div><br></div></div></div><div>This is sharedLinkerFlags.</div></div></blockquote>
</div></div></blockquote><div><br></div></div><div>Whoops this is wrong. Its something different.</div><div class="im"><div> </div><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
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<div><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"><div class="gmail_quote"><div> </div></div></blockquote></div><div>Sorry, I meant configure-time option.<br>
</div></div></blockquote><div><br></div></div><div>Yes, it should be a configure option.</div></div></blockquote><div><br>Actually, I'm guessing that there should be a configure-time option to figure out the platform-dependent<br>
way of exporting symbols as dynamic, and then a compile-time option to actually export the executable's symbols. <br>(Not everybody may want to pollute the dynamic symbol table and, potentially, increase the required symbol search <br>
time).<br><br>Dmitry.<br></div><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"><div class="gmail_quote"><div class="im"><div> </div><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
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<div>Does sharedLinkerFlags alter the behavior of CLINKER?<br></div></div></blockquote><div><br></div></div><div>I thought we fixed LDFLAGS, but maybe not.</div><div><br></div><div> Matt</div><div class="im"><div> </div>
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<div class="gmail_quote"><div>Unless there is another way to link an executable.<br><font color="#888888"><br>Dmitry.<br> <br></font></div><div><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
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Matt</div><div><div> </div><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">Incidentally, currently there appears to be no way to supply additional linker flags, as used to be the case with LDFLAGS.<br>
<font color="#888888">
<br>Dmitry.</font></blockquote></div></div><font color="#888888">-- <br>What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.<br>
-- Norbert Wiener<br>
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</blockquote></div></div><div><div></div><div class="h5"><br><br clear="all"><br>-- <br>What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.<br>
-- Norbert Wiener<br>
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