Is this something new to 2.6, or is it the same as 2.4?
Alan W. Irwin wrote:
The LIST command has issues when dealing with a list with some empty
elements.
To see this try the following CMakeLists.txt
set(list_example "1;;;2;3;4")
message("list_example = ${list_example}")
list(APPEND list_example "5")
message("list_example = ${list_example}")
list(LENGTH list_example list_example_length)
message("list_example_length = ${list_example_length}")
list(GET list_example 1 list_example1)
message("list_example1 = ${list_example1}")
list(REMOVE_AT list_example 5)
message("list_example = ${list_example}")
The result is
list_example = 1;;;2;3;4
list_example = 1;;;2;3;4;5
list_example_length = 5
list_example1 = 2
CMake Error at CMakeLists.txt:5 (list):
list index: 5 out of range (-5, 4)
So APPEND is fine, but LENGTH, GET, and REMOVE_AT work as if the two empty
components of the list are not there.
VARIANT 1.
If I replace the last two lines by
list(REMOVE_AT list_example 1)
message("list_example = ${list_example}")
the result is
list_example = 1;;;2;3;4
list_example = 1;;;2;3;4;5
list_example_length = 5
list_example1 = 2
list_example = 1;3;4;5
VARIANT 2.
If I replace the last two lines by
list(REMOVE_ITEM list_example "1")
message("list_example = ${list_example}")
the result is
list_example = 1;;;2;3;4
list_example = 1;;;2;3;4;5
list_example_length = 5
list_example1 = 2
list_example = 2;3;4;5
VARIANT 3.
If I replace the last two lines by
list(REMOVE_ITEM list_example "")
message("list_example = ${list_example}")
the result is
list_example = 1;;;2;3;4
list_example = 1;;;2;3;4;5
list_example_length = 5
list_example1 = 2
list_example = 1;2;3;4;5
VARIANT 4.
If I replace the last two lines by
list(SORT list_example 1)
message("list_example = ${list_example}")
the result is
list_example = 1;;;2;3;4
list_example = 1;;;2;3;4;5
list_example_length = 5
list_example1 = 2
list_example = 1;2;3;4;5
VARIANT 5.
If I replace the last two lines by
list(REVERSE list_example 1)
message("list_example = ${list_example}")
the result is
list_example = 1;;;2;3;4
list_example = 1;;;2;3;4;5
list_example_length = 5
list_example1 = 2
list_example = 5;4;3;2;1
VARIANT 6.
If I replace the last two lines by
list(FIND list_example "1" one_index)
message("list_example = ${list_example}")
message("one_index = ${one_index}")
the result is
list_example = 1;;;2;3;4
list_example = 1;;;2;3;4;5
list_example_length = 5
list_example1 = 2
list_example = 1;;;2;3;4;5
one_index = 0
VARIANT 7.
If I replace the last two lines by
list(FIND list_example "" null_index)
message("list_example = ${list_example}")
message("null_index = ${null_index}")
the result is
list_example = 1;;;2;3;4
list_example = 1;;;2;3;4;5
list_example_length = 5
list_example1 = 2
list_example = 1;;;2;3;4;5
null_index = -1
VARIANT 8.
If I replace the last two lines by
list(INSERT list_example 4 6 7)
message("list_example = ${list_example}")
the result is
list_example = 1;;;2;3;4
list_example = 1;;;2;3;4;5
list_example_length = 5
list_example1 = 2
list_example = 1;2;3;4;6;7;5
All the above results for LENGTH, GET, REMOVE_AT, REMOVE_ITEM, SORT,
REVERSE, and INSERT are consistent with the mental model that no indices
are
assigned to empty elements of a CMake list, and the result has the empty
elements dropped (which by accident gives the correct result for
REMOVE_ITEM
when an empty element is dropped). However, from the above results APPEND
keeps those empty elements in the result, as does FIND, (but FIND cannot
find those empty elements).
I am not aware of any other language that ignores empty elements or drops
them from the results for certain operations so I believe the above results
are symptoms of a language bug that needs to be addressed. I don't know
CMake well enough to give you a patch, but I assume it is a fairly trivial
fix.
I also have a wishlist bug to report which I hope gets addressed at the
same
time as the more serious bug above.
VARIANT 9.
If I replace the last two lines by
list(INSERT list_example 5 6 7)
message("list_example = ${list_example}")
the result is
list_example = 1;;;2;3;4
list_example = 1;;;2;3;4;5
list_example_length = 5
list_example1 = 2
CMake Error at CMakeLists.txt:21 (list):
list index: 5 out of range (-5, 4)
If you insert just after the end of the list, it should work just like an
append instead of giving you an index error as above.
Alan
__________________________
Alan W. Irwin
Astronomical research affiliation with Department of Physics and Astronomy,
University of Victoria (astrowww.phys.uvic.ca).
Programming affiliations with the FreeEOS equation-of-state implementation
for stellar interiors (freeeos.sf.net); PLplot scientific plotting software
package (plplot.org); the libLASi project (unifont.org/lasi); the Loads of
Linux Links project (loll.sf.net); and the Linux Brochure Project
(lbproject.sf.net).
__________________________
Linux-powered Science
__________________________
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