Introduce a --warn command line option

Replace the singleton --warn-undefined-variables with infrastructure
to manage multiple warnings: the --warn option can take an action
"ignore", "warn", or "error" (which will apply to all warnings), or
a specific warning type and an action for that type.  Multiple
options can be provided and are consolidated.

* NEWS: Announce the new option.
* doc/make.1: Document in the man page.
* doc/make.texi (Warnings): Document in the user's manual.
* Makefile.am: Add new header warning.h.
* src/warning.h: Define enum for actions and warning types, and
macros to test whether they are set.  Keep the default settings
separate so that we can correctly reconstruct MAKEFLAGS.
* src/makeint.h: Remove deprecated warn_undefined_variables_flag.
* src/main.c: Create global variables to hold warning settings.
(switches): Add a new switch for --warn.
(initialize_warnings): Set the default warning actions.
(main): Call initialize_warnings().
(encode_warning_state, decode_warning_state): Convert warning states
between strings and enums.
(encode_warning_name, decode_warning_name): Convert warning names
between strings and enums.
(decode_warn_flags): Convert a --warn option into enum values.  If
deprecated warn_undefined_variables_flag is set convert it to --warn.
(decode_switches): Don't remove duplicates of --warn since order
matters.  Call decode_warn_flags() to handle --warn.
(define_makeflags): Special-case handling of --warn options written
to MAKEFLAGS: write out the current settings.
* src/read.c (tilde_expand): Use new warning control macros.
* src/variable.c (warn_undefined): Ditto.
* src/job.c (construct_command_argv): Ditto.
* tests/scripts/options/warn: Rename from warn-undefined-variables
and add tests for --warn.
* tests/scripts/variables/MAKEFLAGS: Expect the new behavior.

3 files changed, 93 insertions, 56 deletions

diff --git a/tests/scripts/options/warn b/tests/scripts/options/warn
new file mode 100644
index 00000000..98155d46
--- /dev/null
+++ b/tests/scripts/options/warn
@@ -0,0 +1,86 @@
+#                                                                    -*-perl-*-
+
+$description = "Test the --warn option.";
+
+my %warn_test = (
+    '--warn' => '', '--warn=warn' => '', '--warn=error --warn=warn' => '',
+    '--warn --warn=error' => '=error',
+    '--warn=ignore --warn=error --warn=ignore --warn=undefined-var' => '=ignore,undefined-var',
+    '--warn=undefined-var:error --warn' => '=warn,undefined-var:error'
+);
+
+# Verify the deprecated --warn-undefined-variables option
+run_make_test(q!
+$(info MF=$(MAKEFLAGS))
+all:; @#HELPER# env MAKEFLAGS
+!,
+              '--warn-undefined-variables', "MF= --warn=undefined-var\nMAKEFLAGS= --warn=undefined-var");
+
+# Verify parsing of --warn in various forms.
+
+while (my ($f, $r) = each %warn_test) {
+    run_make_test(undef, $f, "MF= --warn$r\nMAKEFLAGS= --warn$r");
+}
+
+# Verify that values set in MAKEFLAGS take effect
+
+while (my ($f, $r) = each %warn_test) {
+    run_make_test(qq!
+MAKEFLAGS += $f
+\$(info MF=\$(MAKEFLAGS))
+all:; \@#HELPER# env MAKEFLAGS
+!,
+                  '', "MF= --warn$r\nMAKEFLAGS= --warn$r");
+}
+
+# Verify that make's special variables don't warn even if they're not set
+run_make_test(q!
+vars := $(.VARIABLES) $(MAKECMDGOALS) $(MAKE_RESTARTS) $(CURDIR)
+vars += $(GNUMAKEFLAGS) $(MAKEFLAGS) $(MFLAGS) $(MAKE_COMMAND) $(MAKE)
+vars += $(MAKEFILE_LIST) $(MAKEOVERRIDES) $(-*-command-variables-*-)
+vars += $(.RECIPEPREFIX) $(.LOADED) $(.FEATURES)
+vars += $(SHELL) $(.SHELLFLAGS) $(MAKE_TERMOUT) $(MAKE_TERMERR)
+vars += $(.DEFAULT) $(.DEFAULT_GOAL) $(-*-eval-flags-*-) $(SUFFIXES)
+vars += $(VPATH) $(GPATH)
+all:;
+!,
+              '--warn=undefined-var', "#MAKE#: 'all' is up to date.");
+
+# sv 63609.
+# Test for buffer overrun in warn_undefined.
+run_make_test(q!
+all:;
+X := $(averyveryveryloooooooooooooooooooooooooooongvariablename)
+!,
+              '--warn=undefined-var',
+              "#MAKEFILE#:3: reference to undefined variable 'averyveryveryloooooooooooooooooooooooooooongvariablename'
+#MAKE#: 'all' is up to date.\n"
+);
+
+# Check undefined variable warnings
+
+# With no options or with ignore, nothing should happen
+run_make_test('
+EMPTY =
+EREF = $(EMPTY)
+UREF = $(UNDEFINED)
+
+SEREF := $(EREF)
+SUREF := $(UREF)
+
+all: ; @echo ref $(EREF) $(UREF)',
+              '', 'ref');
+
+run_make_test(undef, '--warn=undefined-var:ignore', 'ref');
+
+# Check warnings
+run_make_test(undef, '--warn=undefined-var',
+              "#MAKEFILE#:7: reference to undefined variable 'UNDEFINED'
+#MAKEFILE#:9: reference to undefined variable 'UNDEFINED'
+ref");
+
+# Check and errors
+run_make_test(undef, '--warn=undefined-var:error',
+              "#MAKEFILE#:7: *** reference to undefined variable 'UNDEFINED'.  Stop.", 512);
+
+1;
diff --git a/tests/scripts/options/warn-undefined-variables b/tests/scripts/options/warn-undefined-variables
deleted file mode 100644
index d9653d2c..00000000
--- a/tests/scripts/options/warn-undefined-variables
+++ /dev/null
@@ -1,49 +0,0 @@
-#                                                                    -*-perl-*-
-
-$description = "Test the --warn-undefined-variables option.";
-
-$details = "Verify that warnings are printed for referencing undefined variables.";
-
-# Verify that make's special variables don't warn even if they're not set
-run_make_test(q!
-vars := $(.VARIABLES) $(MAKECMDGOALS) $(MAKE_RESTARTS) $(CURDIR)
-vars += $(GNUMAKEFLAGS) $(MAKEFLAGS) $(MFLAGS) $(MAKE_COMMAND) $(MAKE)
-vars += $(MAKEFILE_LIST) $(MAKEOVERRIDES) $(-*-command-variables-*-)
-vars += $(.RECIPEPREFIX) $(.LOADED) $(.FEATURES)
-vars += $(SHELL) $(.SHELLFLAGS) $(MAKE_TERMOUT) $(MAKE_TERMERR)
-vars += $(.DEFAULT) $(.DEFAULT_GOAL) $(-*-eval-flags-*-) $(SUFFIXES)
-vars += $(VPATH) $(GPATH)
-all:;
-!,
-              '--warn-undefined-variables', "#MAKE#: 'all' is up to date.");
-
-# Without --warn-undefined-variables, nothing should happen
-run_make_test('
-EMPTY =
-EREF = $(EMPTY)
-UREF = $(UNDEFINED)
-
-SEREF := $(EREF)
-SUREF := $(UREF)
-
-all: ; @echo ref $(EREF) $(UREF)',
-              '', 'ref');
-
-# With --warn-undefined-variables, it should warn me
-run_make_test(undef, '--warn-undefined-variables',
-              "#MAKEFILE#:7: warning: undefined variable 'UNDEFINED'
-#MAKEFILE#:9: warning: undefined variable 'UNDEFINED'
-ref");
-
-# sv 63609.
-# Test for buffer overrun in warn_undefined.
-run_make_test(q!
-all:;
-X := $(averyveryverylongvariablename)
-!,
-              '--warn-undefined-variables',
-              "#MAKEFILE#:3: warning: undefined variable 'averyveryverylongvariablename'
-#MAKE#: 'all' is up to date.\n"
-);
-
-1;
diff --git a/tests/scripts/variables/MAKEFLAGS b/tests/scripts/variables/MAKEFLAGS
index 32c2ede8..fc18d650 100644
--- a/tests/scripts/variables/MAKEFLAGS
+++ b/tests/scripts/variables/MAKEFLAGS
@@ -99,7 +99,7 @@ all:; \$(info makeflags='\$(MAKEFLAGS)')
 
 # Long options which take no arguments.
 # sv 62514.
-@opts = (' --no-print-directory', ' --warn-undefined-variables', ' --trace');
+@opts = (' --no-print-directory', ' --warn=undefined-var', ' --trace');
 for my $fl (@flavors) {
 for my $opt (@opts) {
 run_make_test("
@@ -139,19 +139,19 @@ all:; \$(info makeflags='\$(MAKEFLAGS)')
 # A mix of multiple flags from env, the makefile and command line.
 # Skip -L since it's not available everywhere
 for my $fl (@flavors) {
-$ENV{'MAKEFLAGS'} = 'ikB --no-print-directory --warn-undefined-variables --trace';
+$ENV{'MAKEFLAGS'} = 'ikB --no-print-directory --warn=undefined-var --trace';
 run_make_test("
 MAKEFLAGS${fl}iknqrswd -Ilocaltmp -Ilocaltmp -Onone -Onone -l2.5 -l2.5
 all:; \$(info makeflags='\$(MAKEFLAGS)')
 ",
 '-Onone -l2.5 -l2.5 -Onone -Ilocaltmp -iknqrswd -i -n -s -k -Ilocaltmp',
-"/makeflags='Bdiknqrsw -Ilocaltmp -l2.5 -Onone --trace --warn-undefined-variables'/");
+"/makeflags='Bdiknqrsw -Ilocaltmp -l2.5 -Onone --trace --warn=undefined-var'/");
 }
 
 # Verify MAKEFLAGS are all available to shell function at parse time.
 for my $fl (@flavors) {
-my $answer = 'Biknqrs -Ilocaltmp -l2.5 -Onone --no-print-directory --warn-undefined-variables';
-$ENV{'MAKEFLAGS'} = 'ikB --no-print-directory --warn-undefined-variables';
+my $answer = 'Biknqrs -Ilocaltmp -l2.5 -Onone --no-print-directory --warn=undefined-var';
+$ENV{'MAKEFLAGS'} = 'ikB --no-print-directory --warn=undefined-var';
 run_make_test("
 MAKEFLAGS${fl}iknqrsw -Ilocaltmp -Ilocaltmp -Onone -Onone -l2.5 -l2.5 --no-print-directory
 \$(info at parse time '\$(MAKEFLAGS)')
@@ -165,8 +165,8 @@ at build time makeflags='$answer'");
 
 # Verify MAKEFLAGS and command line definitions are all available to shell function at parse time.
 for my $fl (@flavors) {
-$ENV{'MAKEFLAGS'} = 'ikB --no-print-directory --warn-undefined-variables';
-my $answer = 'Biknqrs -Ilocaltmp -l2.5 -Onone --no-print-directory --warn-undefined-variables -- hello=world';
+$ENV{'MAKEFLAGS'} = 'ikB --no-print-directory --warn=undefined-var';
+my $answer = 'Biknqrs -Ilocaltmp -l2.5 -Onone --no-print-directory --warn=undefined-var -- hello=world';
 run_make_test("
 MAKEFLAGS${fl}iknqrsw -Ilocaltmp -Ilocaltmp -Onone -Onone -l2.5 -l2.5 --no-print-directory
 \$(info at parse time '\$(MAKEFLAGS)')