Re: Help on Stack trace
Re: Help on Stack trace
- Subject: Re: Help on Stack trace
- From: Arnab Ganguly <email@hidden>
- Date: Fri, 6 Feb 2009 12:28:43 +0530
Hi ,
Thanks for the email and update.What if I use dladdr system call with program counter pointer and fetch the info.dli_sname to get the symbol name?Is it going to be inaccurate or not valid at all?
Regards
-A
On Thu, Feb 5, 2009 at 11:48 PM, Rick Altherr
<email@hidden> wrote:
On Feb 5, 2009, at 6:12 AM, Arnab Ganguly wrote:
Hi All,
Proably the same question I am asking again. atos is fine to use for getting the stack trace.But is it going to be available on all Mac OSX system? What alternative can be taken when atos is not available to get that detailed information.Considering Mac version as Tiger and I have used dladdr and __cxxabiv1::__cxa_demangle but not getting that much clear symbol information compared to atos.My code is on Objective-C.
Thanks
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Just to clarify, a stack trace is a list of addresses that indicate the functions that have been called. It contains no symbolic naming.
atos reads the debugging information in the binaries and returns the symbolic name that contains a given address. The underlying mechanisms for reading the various debugging formats and getting the information correct are quite complex and are very easy to get wrong. I suggest you avoid trying to reimplement them if at all possible.
That said, atos is a developer tool and won't be available on a regular installation of OS X. There isn't really a great solution to this problem. To write a suitable replacement means you would need to:
- Read the dyld loaded images list from the target process (much easier if done from inside the process you are backtracing)
- Read the Mach-O header for each loaded image
- Parse the symbol table (nlist) and STABs (also nlist) from the loaded image
- If the STABs are of a particular format (called Debug Maps), parse the DWARF2 information from the referenced .o's
- If the binary contains a UUID load command, look for a dSYM that has the same UUID
- If a suitable dSYM is found, parse the DWARF2 information contained within
- Adjust the offsets for all the parsed symbol information so they correspond to the load address of the loaded image
- Repeat for each image in the dyld loaded image list
--
Rick Altherr
Architecture and Performance Group
email@hidden
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