make: if a condition is erroneous, skip the whole .if/.endif

make: fix order of error messages in the ":?" modifier

While here: In Var_Parse, EvalStack_Pop needs to be called before
freeing the short-lived variable, as its name is part of the evaluation
stack.

make: use '"filename" line 123' for locations instead of 'filename:123'

The format 'filename:123' is commonly used for identifying a location in
a file. Text editors recognize it and allow quick navigation through it.
The previous format was specific to make and would have required custom
support in editors.

The new format was already used in stack traces, except for the first
line. Now all lines use the same format.

make: add ":" to error message about unknown modifier

In the manual page, the modifiers are listed with a preceding ":", so
use the same pattern in the error message. This removes an inconsistency
between the error messages "Unknown modifier" and "Bad modifier".

make: reduce line length in error messages

The error messages for deeply nested parse errors were hard to decipher,
due to the large amount of text. Split these messages into individual
lines, just as in the backtrace for .include files and .for loops. This
unified backtrace makes the output more uniform.

make: on error, print the targets to be made

This helps to understand situations with several nested sub-makes in
varying directories.

make: add more context information to error messages

In case of a parse error or evaluation error, print the variable value
in addition to the variable name, to see the effects of previous
expression modifiers.

In nested make calls, print the current directory at the bottom of a
stack trace, as that information is otherwise hard to get in a parallel
build spanning multiple directories.

branches: 1.9.2;
make: provide more context information for parse/evaluate errors

tests/make: force line-based diagnostics to be listed in the tests

This way, contradictions between the intended output and the actual
output are closer together and have a better chance of being spotted.

tests/make: extend tests for the ':=' assignment operator

tests/make: test and document .MAKE.SAVE_DOLLARS and ':='

tests/make: finish a previously unfinished sentence in a comment

tests/make: test double indirection in ':=' with undefined variable

Reported by Simon J Gerraty via private mail.

This edge case has been handled in essentially the same way since at
least 2000-05-30, probably several years earlier as well. The test file
is:

---- snip ----
.undef LATER
.undef later
INDIRECT:= ${LATER:S,value,replaced,}
indirect:= ${INDIRECT:C,S,s,}
# expect+1: Unknown modifier "s,value,replaced,"
.if ${indirect} != ""
. error
.else
. warning XXX Neither branch should be taken.
.endif
LATER= uppercase-value
later= lowercase-value
# expect+1: Unknown modifier "s,value,replaced,"
.if ${indirect} != "uppercase-replaced"
. warning XXX Neither branch should be taken.
.else
. error
.endif

all:
@:;
---- snap ----

The output from 'make -r -f later.mk' is:

make-2000.05.30.02.32.21
| make: Unknown modifier 's'
|
| "later.mk", line 9: Need an operator
| make: Unknown modifier 's'
|
| "later.mk", line 15: Need an operator
| Fatal errors encountered -- cannot continue
| exit status 1
make-2000.12.30.16.38.22

The pathnames in the error message gets absolute:

make-2001.01.23.02.48.05
| make: Unknown modifier 's'
|
| ".../later.mk", line 9: Need an operator
| make: Unknown modifier 's'
|
| ".../later.mk", line 15: Need an operator
| Fatal errors encountered -- cannot continue
| exit status 1
make-2001.01.23.02.48.05

All error messages get 'make:' as a common prefix:

make-2001.02.23.21.11.38
| make: Unknown modifier 's'
|
| make: ".../later.mk" line 9: Need an operator
| make: Unknown modifier 's'
|
| make: ".../later.mk" line 15: Need an operator
| make: Fatal errors encountered -- cannot continue
| exit status 1
make-2001.05.29.17.37.52

The 'stopped in' gets added:

make-2001.06.12.23.36.18
| make: Unknown modifier 's'
|
| make: ".../later.mk" line 9: Need an operator
| make: Unknown modifier 's'
|
| make: ".../later.mk" line 15: Need an operator
| make: Fatal errors encountered -- cannot continue
|
| make: stopped in ...
| exit status 1
make-2002.02.21.22.21.34

The empty lines between the error messages get removed.

make-2002.03.21.11.42.21
| make: Unknown modifier 's'
| make: ".../later.mk" line 9: Need an operator
| make: Unknown modifier 's'
| make: ".../later.mk" line 15: Need an operator
| make: Fatal errors encountered -- cannot continue
|
| make: stopped in ...
| exit status 1
make-2009.10.15.02.27.44

The error message for unknown directives gets more helpful:

make-2009.11.19.06.48.37
| make: Unknown modifier 's'
| make: ".../later.mk" line 9: Unknown directive
| make: Unknown modifier 's'
| make: ".../later.mk" line 15: Unknown directive
| make: Fatal errors encountered -- cannot continue
|
| make: stopped in ...
| exit status 1
make-2010.02.22.19.20.33

The directives '.error', '.warning' and '.info' get added:

make-2010.04.29.23.12.21
| make: Unknown modifier 's'
| make: ".../later.mk" line 9: warning: XXX Neither branch should be taken.
| make: Unknown modifier 's'
| make: ".../later.mk" line 15: warning: XXX Neither branch should be taken.
| exit status 0
make-2020.12.20.19.37.23

The error message about an unknown variable modifier gets line number
information:

make-2020.12.20.19.47.34
| make: ".../later.mk" line 6: Unknown modifier 's'
| make: ".../later.mk" line 9: warning: XXX Neither branch should be taken.
| make: ".../later.mk" line 14: Unknown modifier 's'
| make: ".../later.mk" line 15: warning: XXX Neither branch should be taken.
| make: Fatal errors encountered -- cannot continue
| make: stopped in ...
| exit status 1
make-2021.02.23.15.07.58

The error message about an unknown variable modifier gets more context
than only a single letter:

make-2021.02.23.15.19.41
| make: ".../later.mk" line 6: Unknown modifier "s,value,replaced,"
| make: ".../later.mk" line 9: warning: XXX Neither branch should be taken.
| make: ".../later.mk" line 14: Unknown modifier "s,value,replaced,"
| make: ".../later.mk" line 15: warning: XXX Neither branch should be taken.
| make: Fatal errors encountered -- cannot continue
| make: stopped in ...
| exit status 1

make(1): move test result of var-op-expand.mk from exp to mk

This makes it easier to run this test in older versions of make. Empty
output means success.

make(1): add test for edge case in resolving undefined variables

make(1): add dummies for fine-grained tests, one per single feature

The test names have been derived from the current manual page.

All these tests are dummies right now, and the code from the existing
tests will be moved into the new tests step by step.

This is done to prevent modmisc, escape, varmod-edge and varmisc from
growing without any bounds, and to reduce the side-effects of one test
to the others.