Notes
(0037852) Brad King (manager) 2015-01-28 10:36	After macro argument replacement the if() sees if(pipo5) which is false because no such variable is defined to a non-false constant. One can see this by adding set(pipo5 1) before the macro invocation.

(0037853) Brad King (manager) 2015-01-28 10:39	The documentation in the "Macro Argument Caveats" section was added here: Help: Document macro argument caveats in more detail http://cmake.org/gitweb?p=cmake.git;a=commitdiff;h=f0db2e38 [^] and needs to be clarified on this.

(0037858) Daniele E. Domenichelli (developer) 2015-01-29 09:50	This is generated from a wrong expectation that if(${ARGV2}) can be used to tell if an argument was passed or not, but this will give you a wrong result even for a function, not just for a macro. What you want to use here is: if(NOT "${ARGV2}" STREQUAL "") The only difference between functions and macro is that ARGV2 (not expanded) is not defined in a macro, but in a function it will be expanded like a normal variable. This means that there is difference ONLY when you use it without explicitly expanding it. Just to clarify, the following tests: 1. if(ARGV2) 2. if(${ARGV2}) 3. if(NOT ARGV2 STREQUAL "") 4. if(NOT "${ARGV2}" STREQUAL "") 5. if(DEFINED ARGV2) 6. if(DEFINED ${ARGV2}) With the following cases: a. Not passing an argument b. Passing an undefined argument c. Passing an argument that evaluates to TRUE (i.e. set(pipo5 1)) d. Passing an argument that evaluates to FALSE (i.e. set(pipo5 0)) For M. MACRO F. FUNCTION 1aM = 1aF: FALSE (ARGV2 not defined) 2aM = 2aF: FALSE (${ARGV2} evaluates to "" that evaluates to FALSE) 3aM = 3AF: TRUE (ARGV2 is not defined and therefore considered as the string "ARGV2" therefore the "NOT STREQUAL" evaluates to TRUE) 4aM = 4AF: FALSE ("${ARGV2}" evaluates to "" therefore the "NOT STREQUAL" evaluates to FALSE) 5aM = 5aF: FALSE (ARGV2 is not defined) 6aM = 6aF: FALSE (${ARGV2} evaluates to "" that is not defined) * 1bM: FALSE (ARGV2 not defined) * 1bF: TRUE (ARGV2 evaluates to the string "pipo5" that is considered TRUE) 2bM = 2bF: FALSE (pipo5 variable not defined) * 3bM: TRUE (ARGV2 is not defined and therefore considered as the string "ARGV2" therefore the "NOT STREQUAL" evaluates to TRUE) * 3bF: TRUE (ARGV2 evaluates to "pipo5" therefore the "NOT STREQUAL" evaluates to TRUE) 4bM = 4bF: TRUE ("${ARGV2}" evaluates to "pipo5" therefore the "NOT STREQUAL" evaluates to TRUE) * 5bM: FALSE (ARGV2 not defined) * 5bF: TRUE (ARGV2 defined as "pipo5") 6bM = 6bF: FALSE (${ARGV2} evaluates to "pipo5" that is not defined) * 1cM: FALSE (ARGV2 not defined) * 1cF: TRUE (ARGV2 evaluates to the string "pipo5" that is considered TRUE) 2cM = 2cF: TRUE (${ARGV2} evaluates to 1 that is considered TRUE) * 3cM: TRUE (ARGV2 is not defined and therefore considered as the string "ARGV2" therefore the "NOT STREQUAL" evaluates to TRUE) * 3cF: TRUE (ARGV2 evaluates to "1" therefore the "NOT STREQUAL" evaluates to TRUE) 4cM = 4cF: TRUE ("${ARGV2}" evaluates to "1" therefore the "NOT STREQUAL" evaluates to TRUE) * 5cM: FALSE (ARGV2 not defined) * 5cF: TRUE (ARGV2 defined as "pipo5") 6cM = 6cF: TRUE (${ARGV2} evaluates to "pipo5" that is defined as "1") * 1dM: FALSE (ARGV2 not defined) * 1dF: TRUE (ARGV2 evaluates to the string "pipo5" that is considered TRUE) 2dM = 2dF: FALSE (${ARGV2} evaluates to 0 that is considered FALSE) * 3dM: TRUE (ARGV2 is not defined and therefore considered as the string "ARGV2" therefore the "NOT STREQUAL" evaluates to TRUE) * 3cF: TRUE (ARGV2 evaluates to "0" therefore the "NOT STREQUAL" evaluates to TRUE) 4cM = 4cF: TRUE ("${ARGV2}" evaluates to "0" therefore the "NOT STREQUAL" evaluates to TRUE) * 5cM: FALSE (ARGV2 not defined) * 5cF: TRUE (ARGV2 defined as "pipo5") 6cM = 6cF: TRUE (${ARGV2} evaluates to "pipo5" that is defined as "0") The only different behaviours here are 1, 3 (even though for a coincidence the result is always the same), and 5, i.e. the ones where ARGV2 is not explicitly expanded. Note that 2b (the original issue) evaluates to FALSE both in a macro and in a function. Also note that "set(pipo5 xxx)" will change the result of 2 (if set to something that evaluates to TRUE) and 6 (always) BOTH for macro and function. Concluding, I don't think the "Macro Argument Caveats" section is this is misleading... Perhaps a section about how to check if an argument was set should be added both to the macro and function documentation instead?

(0037859) Brad King (manager) 2015-01-29 10:08	Re 0015380:0037858: > Perhaps a section about how to check if an argument was set Yes, that makes sense. Thanks.

(0037932) Daniele E. Domenichelli (developer) 2015-02-06 11:03	Actually I did some more tests and realized that if(NOT "${ARGV2}" STREQUAL "") will not catch an empty ARGV2 (i.e. something like `foo(bar "")`). Moreover in functions if(DEFINED ARGV2) might be true even if the argument was not passed when calling a function from another function. Therefore I believe that the proper way to check if an argument was set is to check the value of the variable ARGC, i.e. if(${ARGC} GREATER 2) I updated the documentation based on my conclusion in the topic "macro-function-docs" Docs: Clarify how to check if an optional arg was passed to macro and function http://www.cmake.org/gitweb?p=stage/cmake.git;a=commitdiff;h=c76592a [^] @Brad can you please review the change?

(0037933) Brad King (manager) 2015-02-06 11:21	Re 0015380:0037932: Thanks. That proposes the wording: ---------------------------------------------------------- A common mistake is to perform tests on the ``ARGV#`` variable in order to check if the ``ARGV#`` variable was passed as an extra argument, but this might cause unexpected results. The recommended way to perform such a check is to test the value of ``${ARGC}``: <example code with lots of wrong cases> ---------------------------------------------------------- This tutorial-like wording does not belong in the reference documentation. Instead the wording describing the ARG* names should be updated to state explicitly that ARGV# beyond ARGC have undefined behavior. While at this, please revise the main documentation paragraph text of macro() and function() to take advantage of reStructuredText markup a bit better.

(0038079) Daniele E. Domenichelli (developer) 2015-02-26 12:18	0015380:0037933: Updated the branch, these are the new commits: Help: Refine the .rst formatting of macro and function documentation http://www.cmake.org/gitweb?p=stage/cmake.git;a=commit;h=e3363bf [^] Help: Clarify that ARGV# beyond ARGC will have an undefined behavior (0015380) http://www.cmake.org/gitweb?p=stage/cmake.git;a=commit;h=4efef3f [^] I also had a look at CMake Modules fixed a few of them that were not checking ARGC and that could have caused an unexpected behaviour if called from inside another function: Check for ARGC before using ARGV# http://www.cmake.org/gitweb?p=stage/cmake.git;a=commit;h=5e76e22 [^]

(0038085) Brad King (manager) 2015-02-26 15:18	Re 0015380:0038079: Thanks. I merged the two Help updates to 'next'. The Modules updates should use if(ARGC GREATER ...) in functions. The if(${ARGC} GREATER ...) idiom is only for macros.

(0038093) Daniele E. Domenichelli (developer) 2015-02-27 09:00	Re 0015380:0038085: Branch updated fixup! Check for ARGC before using ARGV# http://www.cmake.org/gitweb?p=stage/cmake.git;a=commitdiff;h=f9006aa [^] Is there a difference for functions in using "${ARGC}" instead of "ARGC"? I usually choose the first form both in macro and functions, so that I don't have to worry if I switch from macro to function or vice versa.

(0038097) Brad King (manager) 2015-02-27 11:18	Re 0015380:0038093: Thanks. I've squashed your fix in, fixed one typo, and merged the change to 'next' for testing: Modules: Check for ARGC before using ARGV# http://cmake.org/gitweb?p=cmake.git;a=commitdiff;h=a7631fc4 [^] The if() command auto-dereferences variable names. See CMP0054. In a function(), ARGC is an actual variable we should name it to use the if() auto-dereference. In a macro() we have no choice but to use ${ARGC} because it is not really a variable.

(0039085) Robert Maynard (manager) 2015-07-08 08:57	Closing resolved issues that have not been updated in more than 4 months.

Issue History
Date Modified	Username	Field	Change
2015-01-28 10:27	Alina	New Issue
2015-01-28 10:27	Alina	File Added: CMakeLists.txt
2015-01-28 10:36	Brad King	Note Added: 0037852
2015-01-28 10:36	Brad King	Status	new => resolved
2015-01-28 10:36	Brad King	Resolution	open => no change required
2015-01-28 10:39	Brad King	Note Added: 0037853
2015-01-28 10:39	Brad King	Assigned To	=> Daniele E. Domenichelli
2015-01-28 10:39	Brad King	Status	resolved => new
2015-01-28 10:39	Brad King	Resolution	no change required => open
2015-01-28 10:39	Brad King	Summary	Optional arguments for macros are ignored by if() => Misleading documentation in "Macro Argument Caveats" caveats
2015-01-28 10:39	Brad King	Status	new => assigned
2015-01-29 09:50	Daniele E. Domenichelli	Note Added: 0037858
2015-01-29 10:08	Brad King	Note Added: 0037859
2015-02-06 11:03	Daniele E. Domenichelli	Note Added: 0037932
2015-02-06 11:21	Brad King	Note Added: 0037933
2015-02-26 12:18	Daniele E. Domenichelli	Note Added: 0038079
2015-02-26 15:18	Brad King	Note Added: 0038085
2015-02-26 16:34	Stephen Kelly	Relationship added	related to 0013187
2015-02-27 09:00	Daniele E. Domenichelli	Note Added: 0038093
2015-02-27 11:18	Brad King	Note Added: 0038097
2015-02-27 11:18	Brad King	Status	assigned => resolved
2015-02-27 11:18	Brad King	Resolution	open => fixed
2015-02-27 11:18	Brad King	Fixed in Version	=> CMake 3.3
2015-02-27 11:18	Brad King	Target Version	=> CMake 3.3
2015-07-08 08:57	Robert Maynard	Note Added: 0039085
2015-07-08 08:57	Robert Maynard	Status	resolved => closed