The check for matching a file's command to the default rule's command
does not account for null. If no .DEFAULT is defined a rule with no
recipe has it's $< variable set to the value of $@. This breaks second
expansion, particularly when used with pattern rules.
* src/commands.c [set_file_variables]: Check that cmds is set
* tests/scripts/features/se_explicit: Test case
* tests/scripts/features/se_implicit: Test case
Copyright-paperwork-exempt: yes
When merging the variable_set_lists for two targets it could be
that the "from" set list is a subset of the "to" set list: check
for this situation to avoid freeing used memory.
* src/variable.c (merge_variable_set_lists): Walk the "to" list and
if the "from" list is contained in it, nothing to do.
* tests/scripts/features/se_explicit: Add a test.
I decided this feature was too impacting to make the permanent default
behavior. This set of changes makes the default behavior of make the
old behavior (no second expansion). If you want second expansion, you
must define the .SECONDEXPANSION: special target before the first target
that needs it.
This set of changes ONLY fixes explicit and static pattern rules to work
like this. Implicit rules still have second expansion enabled all the
time: I'll work on that next.
Note that there is still a backward-incompatibility: now to get the old
SysV behavior using $$@ etc. in the prerequisites list you need to set
.SECONDEXPANSION: as well.
