How do I handle CMake.exe errors

Question

I have a batch file that starts CMake.exe with some arguments and I need to break the execution if there were any errors in CMake (that's a part of product build process). The problem is that %ERRORLEVEL% from CMake.exe process seems to be always is 0 whereas stadard error output might contain errors such as

...
-- Configuring done
CMake Error at CMakeConfigs/My.cmake:77 (add_library):
  Cannot find source file:

    Resources/ActionIcons/ActionIcon_ABC.png

  Tried extensions .c .C .c++ .cc .cpp .cxx .m .M .mm .h .hh .h++ .hm .hpp
  .hxx .in .txx
Call Stack (most recent call first):
  My/Path/CMakeLists.txt:149 (my_add_target)


-- Generating done
...

I plan to dump standard error output to a file and grep/findstr error, but can error handling be done more elegantly?

Thanks.

Possible duplicate of [How to know whether the cmake project generation ended with success](https://stackoverflow.com/questions/38253153/how-to-know-whether-the-cmake-project-generation-ended-with-success) — Florian, Oct 12 '17 at 12:51
How are we supposed to help you with the batch-file code if you don't provide it in your question? — Squashman, Oct 12 '17 at 13:37

Mofi · Answer 1 · 2019-08-18T13:53:06.777

The most often mistake is using %ERRORLEVEL% in a command block starting with ( and ending with matching ).

The entire command block is preprocessed by Windows command interpreter before running any command in the command block or the IF or FOR command usually used on line with opening (. During this preprocessing all %variable% references are replaced by current values of the referenced environment variables. Then the command block is executed with the preprocessed code.

This behavior can be seen by removing @echo off at top of the batch file, or modify it to @echo on or rem @echo off and run the batch file from within a command prompt window. Now Windows command interpreter outputs to console window every command line and command block after preprocessing as really executed next.

The help of command SET output on running set /? in a command prompt window explains on an IF and a FOR example how to reference an environment variable within a command line or command block modified in same command line or command block on execution using delayed environment variable expansion.

But for this case there is no need for %ERRORLEVEL% expanded during preprocessing phase or delayed expanded using !ERRORLEVEL! at all.

There is the good old IF ERRORLEVEL X ... syntax working since MS-DOS up to currently latest Windows 10.

CMake exits with exit code 0 on success and a greater number on error as nearly all console applications.

IF ERRORLEVEL X ... means IF exit code (return value of function main) assigned to environment variable ERRORLEVEL is greater or equal X THEN ...

Then I suggest to look on:

A successful IF does not modify value of ERRORLEVEL. And EXIT /B without a number also does not modify ERRORLEVEL.

So on next line after the command line running CMake there is only this command line needed to exit the processing of current batch file and return to calling batch file or process on any error encountered by CMake:

if errorlevel 1 exit /B

The calling batch file or process gets the exit code of CMake as a result of the batch file execution because IF and EXIT don't modify ERRORLEVEL in this case. It's really so easy!

How do I handle CMake.exe errors

1 Answers1