From 41adfc6b041474f6985ab72efcfb02b2b64a6b8d Mon Sep 17 00:00:00 2001 From: Brad King Date: Wed, 9 Feb 2022 14:16:50 -0500 Subject: Help: Clarify precedence of AND and OR in 'if' conditions The wording update in commit b74819e4fe (Help: Format 'if' command documentation, 2013-12-18, v3.0.0-rc1~227^2~1) incorrectly implied that `AND` has higher precedence than `OR`. Although this is common in many languages, it has never been true in CMake's implementation. Revise the wording to clarify the precedence. Add a test case demonstrating the order. Fixes: #23207 --- Help/command/if.rst | 23 +++++++++++++++-------- Tests/RunCMake/if/AndOr-stdout.txt | 1 + Tests/RunCMake/if/AndOr.cmake | 6 ++++++ Tests/RunCMake/if/RunCMakeTest.cmake | 2 ++ 4 files changed, 24 insertions(+), 8 deletions(-) create mode 100644 Tests/RunCMake/if/AndOr-stdout.txt create mode 100644 Tests/RunCMake/if/AndOr.cmake diff --git a/Help/command/if.rst b/Help/command/if.rst index a729b1e..4f955db 100644 --- a/Help/command/if.rst +++ b/Help/command/if.rst @@ -38,14 +38,21 @@ The following syntax applies to the ``condition`` argument of the ``if``, ``elseif`` and :command:`while` clauses. Compound conditions are evaluated in the following order of precedence: -Innermost parentheses are evaluated first. Next come unary tests such -as `EXISTS`_, `COMMAND`_, and `DEFINED`_. Then binary tests such as -`EQUAL`_, `LESS`_, `LESS_EQUAL`_, `GREATER`_, `GREATER_EQUAL`_, -`STREQUAL`_, `STRLESS`_, `STRLESS_EQUAL`_, `STRGREATER`_, -`STRGREATER_EQUAL`_, `VERSION_EQUAL`_, `VERSION_LESS`_, -`VERSION_LESS_EQUAL`_, `VERSION_GREATER`_, `VERSION_GREATER_EQUAL`_, -and `MATCHES`_. Then the boolean operators in the order `NOT`_, `AND`_, -and finally `OR`_. + +1. Parentheses. + +2. Unary tests such as `EXISTS`_, `COMMAND`_, and `DEFINED`_. + +3. Binary tests such as `EQUAL`_, `LESS`_, `LESS_EQUAL`_, `GREATER`_, + `GREATER_EQUAL`_, `STREQUAL`_, `STRLESS`_, `STRLESS_EQUAL`_, + `STRGREATER`_, `STRGREATER_EQUAL`_, `VERSION_EQUAL`_, `VERSION_LESS`_, + `VERSION_LESS_EQUAL`_, `VERSION_GREATER`_, `VERSION_GREATER_EQUAL`_, + and `MATCHES`_. + +4. Unary logical operator `NOT`_. + +5. Binary logical operators `AND`_ and `OR`_, from left to right, + without any short-circuit. Basic Expressions """"""""""""""""" diff --git a/Tests/RunCMake/if/AndOr-stdout.txt b/Tests/RunCMake/if/AndOr-stdout.txt new file mode 100644 index 0000000..9fd395b --- /dev/null +++ b/Tests/RunCMake/if/AndOr-stdout.txt @@ -0,0 +1 @@ +-- OR and AND correctly evaluated left to right diff --git a/Tests/RunCMake/if/AndOr.cmake b/Tests/RunCMake/if/AndOr.cmake new file mode 100644 index 0000000..847d6f2 --- /dev/null +++ b/Tests/RunCMake/if/AndOr.cmake @@ -0,0 +1,6 @@ +# AND and OR are the same precedence +if(1 OR 0 AND 0) # equivalent to ((1 OR 0) AND 0) + message(FATAL_ERROR "AND incorrectly evaluated before OR") +else() + message(STATUS "OR and AND correctly evaluated left to right") +endif() diff --git a/Tests/RunCMake/if/RunCMakeTest.cmake b/Tests/RunCMake/if/RunCMakeTest.cmake index 6baa840..de9cb57 100644 --- a/Tests/RunCMake/if/RunCMakeTest.cmake +++ b/Tests/RunCMake/if/RunCMakeTest.cmake @@ -17,3 +17,5 @@ run_cmake(IncompleteMatchesFail) run_cmake(TestNameThatExists) run_cmake(TestNameThatDoesNotExist) + +run_cmake_script(AndOr) -- cgit v0.12