Setting a default symbol path for all DbgHelp programs

If you’re like me, then you have lots of programs you use on a regular basis which utilize DbgHelp to manage symbol access.  Unfortunately, each of these programs typically has its own convention for managing a persisted symbol path, and it can get to be very annoying to update the paths for every single program you use when you need to change your symbol path.

Fortunately, there is a solution:  A little-used (nowadays) environment variable called “_NT_SYMBOL_PATH”.  DbgHelp will add this to the list of symbol paths searched for symbols automatically, without any special configuration needed by programs using it (in most cases; it is possible to programmatically suppress this behavior, but most programs do not do this as it is a bad idea to block this behavior).

How does this environment variable help you consolidate your symbol paths?  Well, there is an option in the System property sheet (under Control Panel) to set default environment variables for your user or the local machine.  You can use this to set a default value for _NT_SYMBOL_PATH for your user, which means that all of your programs using DbgHelp will now have a default symbol search path.

You can give _NT_SYMBOL_PATH any value that you could pass to “.sympath” or save in a WinDbg workspace, including symbol server references.

Note that if you give _NT_SYMBOL_PATH a symbol server reference, you need to make sure that programs using DbgHelp can find symsrv.dll, which means placing it in your path if those programs do not already have a copy in their directories.

2 Responses to “Setting a default symbol path for all DbgHelp programs”

  1. […] Vladimir Scherbina has recently released a useful IDA plugin that enhances IDA’s now built-in support for loading symbols via the symbol server to allow custom symbol server paths. This is something I personally have been wanting for some time; IDA’s PDB loading mechanism overrides _NT_SYMBOL_PATH with a hardcoded value of the Microsoft symbol server. This breaks my little trick for injecting symbol server support into programs that do not already support it, which is fairly annoying. Now, with Vladimir’s plugin, you can have IDA use a custom symbol server without having to hack the PDB plugin and change its hardcoded string constant for the Microsoft symbol server path. (Plus, you can have IDA use your local downstream store cache as well – another disadvantage to how IDA normally loads symbols via PDB.) […]

  2. […] Because kernrate is resolving instruction pointer sampling down to a more granular level than modules (with the “-z” option), you’ll need to tell it how to load symbols for all affected modules (otherwise, the granularity for profiler output will typically be very poor, often restricted to just exported functions). There are two ways to do this. First, you can use the “-j symbol-path” command line option; this option tells kernrate to pass a particular symbol path to DbgHelp for use with loading symbols. I recommend the second option, however, which is to configure your _NT_SYMBOL_PATH before-hand so that it points to a valid DbgHelp symbol path. This relieves you of having to manually tell kernrate a symbol path every time you execute it. […]