[Bug ld/1150] undefined reference to `_mpi_sgi_init'

[michael at weiser dot dinsnail dot net]

------- Additional Comments From michael at weiser dot dinsnail dot net  
2005-11-09 13:24 -------
I don't have any information beyond the error message and what I learned from
the message to the mailing list quoted above. The behaviour of OPTIONAL symbols
seems to be that they're silently ignored if not present in any of the linked
objects, allowing for using libraries if linked against but working anyway if
missing. In the case of libpthread this seems to silently recognize linkage
against mpi and doing a call into mpi to make it aware of pthreads being used
(or the like).

Some googling reveals the following resources on optional symbols:

64-bit ELF Object File Specification:
http://techpubs.sgi.com/library/manuals/4000/007-4658-001/pdf/007-4658-001.pdf
#pragma optional in MIPSpro cc:
http://techpubs.sgi.com/library/tpl/cgi-bin/getdoc.cgi?coll=0650&db=bks&srch=&fname=/SGI_Developer/Pragmas/sgi_html/ch07.html
optionalsym:
http://biology.ncsa.uiuc.edu/cgi-bin/infosrch.cgi?cmd=getdoc&db=man&fname=/usr/share/catman/u_man/cat1/optionalsym.z
mips st_other and STO_OPTIONAL:
http://koolkat2.cs.rice.edu/cgi-bin/cvsweb.cgi/Open64/osprey1.0/linux/include/Attic/elf.h?rev=1.2

Especially the 64-bit Object File Specification seems to contain quite some
background on this.

BTW: I encountered the problem with a gcc-4.0.1 configured with --with-abi=64
when compiling and linking 64 bit objects/executables.

-- 


http://sourceware.org/bugzilla/show_bug.cgi?id=1150

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