diff options
| -rw-r--r-- | Source/cmIfCommand.h | 59 |
1 files changed, 25 insertions, 34 deletions
diff --git a/Source/cmIfCommand.h b/Source/cmIfCommand.h index 107a892..7c4baba 100644 --- a/Source/cmIfCommand.h +++ b/Source/cmIfCommand.h @@ -125,10 +125,13 @@ public: "True if the constant is 1, ON, YES, TRUE, Y, or a non-zero number. " "False if the constant is 0, OFF, NO, FALSE, N, IGNORE, \"\", " "or ends in the suffix '-NOTFOUND'. " - "Named boolean constants are case-insensitive." + "Named boolean constants are case-insensitive. " + "If the argument is not one of these constants, " + "it is treated as a variable:" "\n" " if(<variable>)\n" - "True if the variable's value is not a false constant." + "True if the variable is defined to a value that is not a false " + "constant. False otherwise. " "\n" " if(NOT <expression>)\n" "True if the expression is not true." @@ -199,38 +202,26 @@ public: "that contains them." "\n" - "The if statement was written fairly early in CMake's history " - "and it has some convenience features that are worth covering. " - "The if statement reduces operations until there is " - "a single remaining value, at that point if the case " - "insensitive value is: ON, 1, YES, TRUE, Y it returns true, if " - "it is OFF, 0, NO, FALSE, N, NOTFOUND, *-NOTFOUND, IGNORE it " - "will return false. \n" - - "This is fairly reasonable. The convenience feature that sometimes " - "throws new authors is how CMake handles values that do not " - "match the true or false list. Those values are treated as " - "variables and are dereferenced even though they do not have " - "the required ${} syntax. This means that if you write\n" - - " if (boobah)\n" - - "CMake will treat it as if you wrote \n" - - " if (${boobah})\n" - - "likewise if you write \n" - - " if (fubar AND sol)\n" - - "CMake will conveniently treat it as \n" - - " if (\"${fubar}\" AND \"${sol}\")\n" - - "The later is really the correct way to write it, but the " - "former will work as well. Only some operations in the if " - "statement have this special handling of arguments. The " - "specific details follow: \n" + "The if command was written very early in CMake's history, predating " + "the ${} variable evaluation syntax, and for convenience evaluates " + "variables named by its arguments. " + "Note that normal variable evaluation with ${} applies before the " + "if command even receives the arguments. " + "Therefore code like\n" + " set(var1 OFF)\n" + " set(var2 \"var1\")\n" + " if(${var2})\n" + "appears to the if command as\n" + " if(var1)\n" + "and is evaluated according to the if(<variable>) case " + "documented above. " + "The result is OFF which is false. " + "However, if we remove the ${} from the example then the command sees\n" + " if(var2)\n" + "which is true because var2 is defined to \"var1\" which is not " + "a false constant." + "\n" + "Automatic evaluation applies in the other cases as follows:\n" "1) The left hand argument to MATCHES is first checked to see " "if it is a defined variable, if so the variable's value is " |