Problem spawning application

Gosh, this is so weird, I don't know what to say. The short version is that I have a simulator app which I spawn from my application when the user asks me to. It recently stopped working, though I can run the simulator fine from the command line or Start menu. This could be due to moving to VS2010 or Windows 7 or something I didn't notice reviewing source control diffs.

I have a second simulator which I try to spawn in the same fashion and it works fine.

By default, I'm using Qt3's QProcess wrapper around CreateProcess for this purpose, but I get the same behavior using system, my own CreateProcess, and ShellExecute.

ShellExecute of a cmd.exe "/c application params" does provide me with some more information however. I get the dialog

"The program can't start because MSVCR80.dll is missing from your computer. Try reinstalling the program to fix this problem."

Inconveniently, both the parent application and the second simulator use MSVCR80.dll.

Upon copying MSVC*80.dll from g:\windows\winsxs\x86_microsoft.vc80.crt_1f开发者_高级运维c8b3b9a1e18e3b_8.0.50727.4927_none_d08a205e442db5b5 to the same directory as my executable, the error message changes to

"Runtime Error!

Program: g:\path\to\app.exe

R6034

An application has made an attempt to load the C runtime library incorrectly.

Please contact the application's support team for more information.

Followed by

The application was unable to start correctly (0xc0000142). Click OK to close the application.

And, once again, the application runs fine from the command line with those dlls in place.

Update:

I suspected perhaps it was environment related, so changed my ShellExecute mechanism to do cmd /c set && app params. I set up a cmd.exe with those same params and my app is now crashing similarly. Will update when I figure out why :)

It is MATLAB's component runtime tool that is modifying my process's PATH variable to bad effect. It is prepending its own dir full of dll's and wreaking havoc.

A foolish tool I was using did a setenv on PATH, prepending a directory it wanted for dynamically loading some dlls, but which messed up my application later. I ended up using GetEnvironmentStrings as shown in the last example here, erasing the first entry in the PATH env var, and sending the new (original) environment to QProcess, which wraps CreateProcessA.

You need to install the CRT

This may work - if it breaks, you get to keep both pieces :-)

Try installing VC++ redistributable from here - http://www.microsoft.com/downloads/en/details.aspx?familyid=A5C84275-3B97-4AB7-A40D-3802B2AF5FC2&displaylang=en.

Remember to backup your system, create a restore point etc. before installing stuff.

Another idea -try reinstalling the failing appliacation itself. It may come with its own copy of VC++ redistributables, and reinstalling might help. Esp. trying to reinstall it using Windows 7's compability mode (perhaps go back to Vista or XP compatibility) might be even more effective.

To reiterate - you'll have to try, and I've no real idea if either of the above ideas will do you good, or even be sure to do no harm. That said, if I were faced with a similar problem, these are the steps I'd try. HTH!