cmake config_error ai_generated true

CMake Error: if given arguments: "VAR" "STREQUAL" "value" Unknown arguments specified

ID: cmake/variable-not-defined-in-if

Also available as: JSON · Markdown · 中文
95%Fix Rate
87%Confidence
1Evidence
2023-08-10First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
CMake 3.10 active — — —
CMake 3.16 active — — —
CMake 3.22 active — — —
CMake 3.27 active — — —

Root Cause

Using a variable name without ${} in a CMake if() condition, causing CMake to treat it as a literal string instead of expanding it.

generic

中文

在 CMake if() 条件中使用了变量名但没有加 ${}，导致 CMake 将其视为字面字符串而不是展开变量。

Official Documentation

https://cmake.org/cmake/help/latest/command/if.html

Workarounds

  1. 95% success Use ${VAR} in the if() condition to expand the variable. 
    Use ${VAR} in the if() condition to expand the variable.
  2. 90% success Alternatively, use if(DEFINED VAR) to check if the variable is defined, then use ${VAR} in comparisons. 
    Alternatively, use if(DEFINED VAR) to check if the variable is defined, then use ${VAR} in comparisons.

中文步骤

  1. Use ${VAR} in the if() condition to expand the variable.
  2. Alternatively, use if(DEFINED VAR) to check if the variable is defined, then use ${VAR} in comparisons.

Dead Ends

Common approaches that don't work:

  1. Adding quotes around the variable: if("${VAR}" STREQUAL "value") 10% fail

    Quoting the variable expansion is fine, but the real issue is forgetting ${}. This workaround actually works if the variable is defined, but it's a style issue.

  2. Removing the STREQUAL keyword and using if(VAR value) thinking it's a different syntax 95% fail

    CMake does not support if(VAR value) as a comparison; it will either error or give unexpected results.

  3. Defining the variable with set(VAR "value") but still using bare VAR in if() 80% fail

    Even if the variable is defined, bare VAR in if() checks if the literal string 'VAR' is defined, not the variable's value.