HELP! pstack description...

[williechoi]

I'm new to this forum and I just started to used "pstack". However, can
anyone tell me how to read the pstack? Like I know the first set of
number is the return address of the function and then is the function
name and I dont know the rest of it? What does those 6 paramters stand
for and what about the last number with a + sign infront of it??? The
following is an example....please help!!


----------------- lwp# 3 / thread# 11 --------------------
0002b608 _ZN10imaSPAgent10OpenStreamEPiR15imaQueryProcDef (0, fd70d28c,
10de00, fef3569c, 0, cf7a8) + 6b8
0002c3c4 _ZN10imaSPAgent4ExecEPiR15imaQueryProcDef (0, fd70d28c,
10de00, 106e6c, 0, fefa33dc) + 1c
0002edd0 _ZN12imaSPManager12RunProcedureEPiR15imaQueryProcD ef
(fd70d6a8, fd70d494, 10de00, 14e46c, 0, 0) + 178
000264cc _ZN10imaQuerySP7ExecuteER10imaMessage (fd70d6a8, fd70d618,
fd70d5a0, fd70d648, 181d2c, 85934) + 115c
000327f0 _Z18QueryMgrThreadProcPv (ffbefa78, fe7b4798, 0, 5, 1,
fe401000) + 1390
fe79bad0 _thread_start (ffbefa78, 0, 0, 0, 0, 0) + 40

--
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[Andrew Gabriel]

In article <3170236.1059662837@dbforums.com>,
williechoi <member34679@dbforums.com> writes:

>
> I'm new to this forum and I just started to used "pstack". However, can
> anyone tell me how to read the pstack? Like I know the first set of
> number is the return address of the function and then is the function
> name and I dont know the rest of it? What does those 6 paramters stand
> for and what about the last number with a + sign infront of it??? The
> following is an example....please help!!

It would really help if you said which OS and which processor.
I'm guessing this is Solaris on sparc, and if it isn't, my
answer is garbage (might be garbage anyway;-)

The 6 parameters are the function call parameters.
sparc gives you 6 function call parameters for free due to
the way it's register windows work. If your function took
less than 6, then the extras are undefined. If it took more
than 6, the extras are on the stack and not shown.
There's a nasty gotcha here though. The values displayed
are the _current_ values of the registers, and it's possible
that the function itself will have reused these registers for
something else, so they may no longer hold the original entry
values. You would have to disassemble the function to see if
it was reusing one of the registers as local workspace.
The '+' value is how far into the function it got before,
typically, calling the function listed above.

> ----------------- lwp# 3 / thread# 11 --------------------
> 0002b608 _ZN10imaSPAgent10OpenStreamEPiR15imaQueryProcDef (0, fd70d28c,
> 10de00, fef3569c, 0, cf7a8) + 6b8
> 0002c3c4 _ZN10imaSPAgent4ExecEPiR15imaQueryProcDef (0, fd70d28c,
> 10de00, 106e6c, 0, fefa33dc) + 1c
> 0002edd0 _ZN12imaSPManager12RunProcedureEPiR15imaQueryProcD ef
> (fd70d6a8, fd70d494, 10de00, 14e46c, 0, 0) + 178
> 000264cc _ZN10imaQuerySP7ExecuteER10imaMessage (fd70d6a8, fd70d618,
> fd70d5a0, fd70d648, 181d2c, 85934) + 115c
> 000327f0 _Z18QueryMgrThreadProcPv (ffbefa78, fe7b4798, 0, 5, 1,
> fe401000) + 1390
> fe79bad0 _thread_start (ffbefa78, 0, 0, 0, 0, 0) + 40

At offset 40 into thread start(), it called
_Z18QueryMgrThreadProcPv (ffbefa78, fe7b4798, 0, 5, 1,fe401000),
and at 1390 into _Z18QueryMgrThreadProcPv(), it called
_ZN10imaQuerySP7ExecuteER10imaMessage (fd70d6a8, fd70d618, fd70d5a0, fd70d648, 181d2c, 85934)
etc.
Again, note the shown parameters are not necessarily what was really
passed. I presume you also need to do some function name demangling
to get the real function names.

--
Andrew Gabriel
Consultant Software Engineer

[Bjorn Reese]

williechoi wrote:

>
> I'm new to this forum and I just started to used "pstack". However, can
> anyone tell me how to read the pstack? Like I know the first set of
> number is the return address of the function and then is the function
> name and I dont know the rest of it? What does those 6 paramters stand
> for and what about the last number with a + sign infront of it??? The

pstack is a low-level debugging tool. It does not know the signature
of your functions, that is it does not know how many arguments your
functions take, so it simply displays the six first values found
on the stack. Furthermore, it does not know C++ name mangling, so
your function names look funny. You have to decipher them yourselves
(by qualified guessing from the legible names).

> ----------------- lwp# 3 / thread# 11 --------------------
> 0002b608 _ZN10imaSPAgent10OpenStreamEPiR15imaQueryProcDef (0, fd70d28c,
> 10de00, fef3569c, 0, cf7a8) + 6b8
> 0002c3c4 _ZN10imaSPAgent4ExecEPiR15imaQueryProcDef (0, fd70d28c,
> 10de00, 106e6c, 0, fefa33dc) + 1c

In general, in C++ the 'this' pointer is passed as the first argument
(although you do not see this in the C++ sourcecode.) As the first
argument is zero in the above line, there is a good chance that you
have called a method on an uninstantiated object in the function
below.

> 0002edd0 _ZN12imaSPManager12RunProcedureEPiR15imaQueryProcD ef
> (fd70d6a8, fd70d494, 10de00, 14e46c, 0, 0) + 178
> 000264cc _ZN10imaQuerySP7ExecuteER10imaMessage (fd70d6a8, fd70d618,
> fd70d5a0, fd70d648, 181d2c, 85934) + 115c
> 000327f0 _Z18QueryMgrThreadProcPv (ffbefa78, fe7b4798, 0, 5, 1,
> fe401000) + 1390
> fe79bad0 _thread_start (ffbefa78, 0, 0, 0, 0, 0) + 40