Pstack showing "??????" in place of function name

Question

I am using solaris 5.10 kernel patch Generic_127127-11
When I do pstack on a core file it shows following output
----------------- lwp# 11 --------------------------------
001b8d88 ???????? (14c0fb90, 14c50c70, 8, fe3fb9b4, 0, 0)
00199964 ???????? (0, 148db224, 148db224, 0, c, 0)
00196b30 ???????? (ffffffff, 449d3, 7a2dc2, 36, fe3fba9c, 0)
00176eec ???????? (12a8b4a0, 1, 176e10, 0, 0, 0)
001d7210 ???????? (0, 0, 1300678, 0, 0, 0)
001da740 ???????? (12797c0, 899028, 897800, ffffc2f7, f423f, fff0bdc0)
001a7ec0 ???????? (ffffffff, 0, 0, 0, 0, 0)
001a7e20 ???????? (0, 0, 0, 0, 0, 0)
000e3c68 ???????? (117d5c0, fe3fbdb8, 0, 117bea0, fe3fbd8c, 13880)
000caab4 ???????? (117bd50, ca3a4, 471e2c, fe3fbd98, feef1818, 0)
00471ed8 ???????? (117bd50, 471ea0, 6203b0, ff000000, fec64a00, 0)
00485674 ???????? (117b0b0, 485624, 0, 89cc00, 0, fec64a00)
004855e4 ???????? (117b0b0, 906d48, 0, 0, fec64a00, 1)
Is there any specific reason for "??????" in place of function names ?
Is is possible that core file is not written completely ?
If yes, what can be done to make core file be written completely ?

Answer 1

You are asking on a wrong forum: if you really hit pstack problem, there's no one here to help you, as pstack is Solaris utility. It does not belong to Sun Studio. It's better to post to one of OpenSolaris forums, for example, this one: http://www.opensolaris.org/jive/forum.jspa?forumID=9
However, in this case I guess I can answer your question: ??? instead of function names appear when pstack can't map address of particular PC (0x001b8d88 for example) to a symbol.
Symbols are located in two separate sections of executable/shared library: .symtab and .dynsym. The former is used to (this is very rough description) find names when linking object (*.o) files and is not needed at run time. .dynsym is used at run time to find symbols referenced by name, which are usually in the other library (like "printf" symbol, for example).
pstack can use both .symtab and .dynsym, provided that they can be found. .symtab is not present in memory image of the process from which core file is generated, so pstack needs original executable file to be available to read .symtab (you can ask the system to pull symtab from files at the time core is generated using coreadm -I defaultsymtab+ command; see coreadm(1M)). Also, many build scripts remove symbol table from final executable (by using strip(1), for example).
In terms of C++ (again, rough description), all functions end up in .symtab and only non-local functions are present both in .symtab and .dynsym. So there are fewer chances for a static function to have a name in a.out than for an extern function.
To summarize, pstack can print ??? instead of symbol name because either (or combination) of
- absence of original executable (NB: it should be at the same place; core file may contain relative path to executable!);
- stripped executable and ??? symbols are all local (static) functions;
- mismatch of some kind (core file refers to a.out, but a.out there is different so addresses does not make sense anymore);
- missing information in core file (see coreadm(1M)),
- corrupted core file (theoretically, if core was corrupted during write, it should have PF_SUNW_FAILURE flag in pflag core output, but I have no personal experience here).