Commands that manipulate test properties are especially fragile, since many test properties accept lists and therefore must be quoted to pass through to the command correctly. A number of the property-setting commands expect alternating key/value pairs in their argument lists. In some cases, dropping empty items or flattening embedded lists can actually be helpful, but this is often not the case.įor commands that handle arbitrary properties directly, this is a risky area.
Use ARGV and ARGN for forwarding only in scenarios where it can be guaranteed that neither of these two behaviors will cause problems.
In order to configure cmake before installation, run command below./configure -prefix/opt/cmake. When used to forward arguments, list flattening causes empty strings to be discarded and embedded semicolons will become argument separators. Configuration: If you want to see the available conifuration options, run command below./configure -help. Closing Remarksīe aware of the limitations of ARGV and ARGN. Therefore, implementors need to consider whether the command being forwarded to is likely to receive options of that nature in the future before committing to using ARGV and ARGN for forwarding arguments. If you were especially unlucky, it might not lead to an error, but instead to a silent change in behavior. If that were to occur, then an implementation using the above argument-forwarding technique would no longer pass through those arguments safely. While find_package() might not take any arguments that could have an embedded semicolon with the current CMake release, there’s nothing to say that support for such an option might not be added in the future. Therefore, the method used in the original example should be okay for forwarding arguments to that command. Returning briefly to our first example, one might raise the point that the find_package() command doesn’t have any arguments that could/should contain a semicolon and any empty strings can safely be dropped. Using the above named arguments yields the output: foo P1 = 'abc', P2 = '123', P3 = ''
CMAKE COMMAND FULL
Internally, CMake collapses the full set of arguments into a single list and then assigns them firstly to the named arguments of the called function, and then any remaining leftover arguments are made available to the function as the $'") In its attempt to forward the caller’s arguments to the original implementation of find_package(), the above is making use of the way CMake implements function arguments. The same example from the previous article will serve as our starting point: macro(find_package) We now look at a related but more subtle problem associated specifically with forwarding command arguments. That article highlighted the dangers of trying to override a function and forward the call to the original implementation. The previous article discussed an example from Dan Pfeifer’s popular Effective CMake talk.
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