基于 Qt 的 C++ 项目如果从 cmd.exe 运行但不能从 Qt Creator 中运行，则可以工作

Question

I am writing a very minimal C/C++ Qt-based application for Windows (only Windows -- not cross platform at all) that uses a VISA library (visa64.dll) to talk to some external hardware. That library, in turn, uses some other libraries:

(screenshot from Dependency Walker aka depends.exe)

Originally I wrote it in Visual Studio and it worked great. Then I ported it to Qt Creator (using Qt5, w/ MSVC 2015 Visual C++ toolchain) and I got runtime errors. It knows where to find the external header files, so I think my INCLUDEPATH is right, and it builds fine so I think the LIBS variables in my.pro file are right, which is to say it can find the.lib files it needs. However, the first API I call from this external library ( viOpenDefaultRM ) returns the following error: VI_ERROR_LIBRARY_NFOUND . This happens whether I make a debug build or a release build, and whether or not I am running it with a debugger. As long as I run the program from within Qt Creator, it gets runtime errors.

Here is my.pro file:

TEMPLATE = app
CONFIG += console c++11
CONFIG -= app_bundle
CONFIG -= qt

SOURCES += main.cpp

INCLUDEPATH += $$PWD/'../../../../Program Files/IVI Foundation/VISA/Win64/Include'

LIBS += -L$$PWD/'../../../../Program Files/IVI Foundation/VISA/Win64/Lib_x64/msc/' -lvisa64

INCLUDEPATH += $$PWD/'../../../../Program Files/IVI Foundation/VISA/Win64/Include'
DEPENDPATH += $$PWD/'../../../../Program Files/IVI Foundation/VISA/Win64/Include'

The paths that end with /Include have header (.h) files (it's a C library), and the path that ends with /msc has a.lib file. The.lib files are not static libraries, they are the interface files for some corresponding DLLs. Those DLL files are in C:\System32 . There are also 32-bit versions in C:\SysWOW64 . They may also exist elsewhere but if they do I am not aware of it.

Now, if I run it from cmd.exe it works fine. That is, if I open a cmd.exe terminal window and navigate to my Qt project's build directory ( c:\blah\blah\blah\obj\debug\ ) and run the executable from cmd.exe, I get no runtime errors. It can connect to the external hardware, talk to it, all good things are happening, much rejoicing.

I've done a decent amount of searching and researching about this problem, and I am somewhat cursed by the fact that most people have the opposite problem, which means that problem (the opposite one of mine) is what turns up in Google/DuckDuckGo/StackOverflow/forum.qt.io/doc.qt.io searches. That problem usually has to do with missing/misplaced Qt libraries. Here is an example. The answer to this question usually ends up with a link to a page on how to deploy Qt projects for Windows, eg this article .

Also I've read this article from Qt on how to add libraries to your project, and it didn't help me out, but I could be missing something and/or doing it wrong.

This might be something really dumb I'm missing and frankly I hope it is. Thanks*10^6.

Answer 1

TL;DR: The kit I was using to compile in Qt Creator had a different PATH set than my system PATH . To fix this, I did echo %PATH in cmd.exe and copied all the stuff that had to do with the drivers I'm trying to use into the PATH for the kit I'm using in Qt Creator. More details below.

I got this to work this morning. As suggested by @adrien-lerevat, when run from within Qt Creator, my executable couldn't find some DLLs it needed. The long and short of it is that I was defining a PATH in my kit (a "kit" in Qt is basically a compiler, a debugger, and some environment variables) that was different from, and not a superset of, my normal system path. I had inherited this kit for other purposes, you see, from other projects, and I didn't realize a PATH could be set in it, or that I was setting one. So to find the PATH I was setting for Qt Creator, I went to the Tools dropdown and selected Options... , then Build & Run , then Kits . Then click on the kit you are using to edit it. As such:

That should give you a list of stuff, one thing of which is called Environment . That should have a Change... button you can press:

which should open a new window with all your environment stuff:

(screenshot is from after I fixed the problem)

This is where I found PATH , as well as some library and include paths that were worth knowing about. So now that I knew what my Qt Creator PATH was, I opened cmd.exe and typed the command echo %PATH% to find out what my system PATH was. I grabbed everything that had to do with these VISA drivers I'm using (basically anything with VISA and/or IVI Foundation in the path) and pasted them into my PATH in Qt Creator. This was the list of stuff I pasted in there to make it work:

C:\WINDOWS\system32;C:\Program Files\IVI Foundation\VISA\Win64\ktvisa;C:\Program Files\IVI Foundation\VISA\Win64\bin;C:\Program Files (x86)\IVI Foundation\VISA\WinNT\bin;C:\Program Files (x86)\IVI Foundation\VISA\WinNT\Bin\;C:\Program Files\IVI Foundation\VISA\Win64\Bin\;C:\Program Files (x86)\IVI Foundation\VISA\winnt\agvisa;C:\Program Files\Keysight\IO Libraries Suite\bin;C:\Program Files (x86)\Keysight\IO Libraries Suite\bin;C:\Program Files (x86)\IVI Foundation\VISA\WinNT\ktvisa;C:\Program Files (x86)\IVI Foundation\IVI\bin;C:\Program Files\IVI Foundation\IVI\bin;

I added c:\system32 because I know that's where visa64.dll is, which is at least one top-level DLL I know I need. Oddly enough, though, when I added just c:\system32 without all the VISA and IVI Foundation stuff, that didn't work. So, I don't know if everything I added to my Qt Creator path was necessary, as I've just come upon this solution, but once I pare down the list to find out what all I actually needed I will add that information here. Just in case anyone else ever comes across this problem or is curious. And for the sake of completeness I suppose. Okay thanks everyone;)