Question

I am compiling an iPhone application via command line (so no Xcode options involved) however I am unable to get my symbol names to show when profiling with Instruments.

I have tried several flags such as -gdawrf-2 and -g without any success. I have also tried using dsymutil to generate a .dSYM file but I have no clue how I’m supposed to use it so that failed as well.

Answer 1

How Instruments obtains debug information:

Instruments obtains debug info from a .dSYM file which is normally generated automatically by XCode when setting Debug Information Format to DWARF with dSYM File combined with a checkmark in the Generate Debug Symbols option box. Setting these options will add an extra step to the XCode build process and generate a dSYM file after the application has been compiled. Every dSYM is built with a UUID that corresponds to a UUID in a Mach-O section in the binary that it’s derived from. A Spotlight importer indexes the UUIDs of every dSym file that is in a Spotlight-accessible location on your Mac. Therefore SPOTLIGHT does all the black magic and is responsible of making the link between the .app you are running and its corresponding .dSYM file.

How to generate debug information and dSYM file without XCode:

Make sure you are compilig with –gdwarf-2 and -g flags. (Other flag combinations might work)

-g
Produce debugging information in
the operating system’s native format
(stabs, COFF , XCOFF , or DWARF 2).
GDB can work with this debugging
information. On most systems that use
stabs format, -g enables use of extra
debugging information that only GDB
can use; this extra information makes
debugging work better in GDB but will
probably make other debuggers crash or
refuse to read the program. If you
want to control for certain whether to
generate the extra information, use
-gstabs+, -gstabs, -gxcoff+, -gxcoff, or -gvms (see below). GCC allows
you to use -g with -O. The shortcuts
taken by optimized code may
occasionally produce surprising
results: some variables you declared
may not exist at all; flow of control
may briefly move where you did not
expect it; some statements may not be
executed because they compute
constant results or their values were
already at hand; some statements may
execute in different places because
they were moved out of loops.
Nevertheless it proves possible to
debug optimized output. This makes it
reasonable to use the optimizer for
programs that might have bugs.

-gdwarf-2
Produce debugging information in DWARF version 2 format
(if that is supported). This is the
format used by DBX on IRIX 6. With
this option, GCC uses features of
DWARF version 3 when they are useful;
version 3 is upward compatible with
version 2, but may still cause
problems for older debuggers.

Generate a dSYM file using dsymutil. If the tool isn’t recognized in command line, use spotlight to find it.
IMPORTANT: Place .app file on your mac HD before you generate the dSYM if you are working on a networked drive.

dsymutil MyApp.app/MyApp -o
MyApp.app.dSYM

Place the .dSYM file on the mac’s local drive and run Instruments as you normally would.

Resettig spotlight’s indexing:

If symbols aren’t shown, it might be because spotligh is bugged. You can try reseting spotlight’s indexing by adding your folder containing the dSYM file (or even your drive) to the “Prevent spotlight from searching these locations” in the spotlight preferences and then removing it right away.