Add a new --undef command-line option

This option allows to disable the generation of macro tags from #undef
directives, see PR #221 for the rationale. The default behaviour is
unchanged, i.e. a tag is still generated.

The help and man have been updated accordingly, and I added a small unit
to check that --undef=no disables the generation of a tag. The
directives.c unit already checks that a tag is generated when no option
is passed (which is equivalent to --undef=yes).

Units/option-disable-undef.c.t/args.ctags

@@ -0,0 +1 @@
+--undef=no

Units/option-disable-undef.c.t/expected.tags

@@ -0,0 +1 @@
+MACRO_TO_SEE	input.c	/^#define MACRO_TO_SEE$/;"	d	file:

Units/option-disable-undef.c.t/input.c

@@ -0,0 +1,2 @@
+#define MACRO_TO_SEE
+#undef MACRO_NOT_TO_SEE

ctags.1

@@ -790,6 +790,12 @@ Prints statistics about the source files read and the tag file written during
 the current invocation of \fBctags\fP. This option is off by default.
 This option must appear before the first file name.
 
+.TP 5
+\fB\-\-undef\fP[=\fIyes\fP|\fIno\fP]
+Specifies whether a macro tag should be generated from an #undef CPP directive
+(in a C/C++ file), as if it were a #define directive. This option is enabled by
+default.
+
 .TP 5
 \fB\-\-verbose\fP[=\fIyes\fP|\fIno\fP]
 Enable verbose mode. This prints out information on option processing and a

get.c

@@ -328,6 +328,18 @@ static void directiveDefine (const int c)
 	Cpp.directive.state = DRCTV_NONE;
 }
 
+static void directiveUndef (const int c)
+{
+	if (Option.undef)
+	{
+		directiveDefine (c);
+	}
+	else
+	{
+		Cpp.directive.state = DRCTV_NONE;
+	}
+}
+
 static void directivePragma (int c)
 {
 	if (isident1 (c))
@@ -412,7 +424,7 @@ static boolean handleDirective (const int c)
 		case DRCTV_HASH:    ignore = directiveHash (c);  break;
 		case DRCTV_IF:      ignore = directiveIf (c);    break;
 		case DRCTV_PRAGMA:  directivePragma (c);         break;
-		case DRCTV_UNDEF:   directiveDefine (c);         break;
+		case DRCTV_UNDEF:   directiveUndef (c);         break;
 	}
 	return ignore;
 }

options.c

@@ -158,6 +158,7 @@ optionValues Option = {
 	NULL,       /* --etags-include */
 	DEFAULT_FILE_FORMAT,/* --format */
 	FALSE,      /* --if0 */
+	TRUE,       /* --undef */
 	FALSE,      /* --kind-long */
 	LANG_AUTO,  /* --lang */
 	TRUE,       /* --links */
@@ -259,7 +260,7 @@ static optionDescription LongOptionDescription [] = {
  {1,"  --help"},
  {1,"       Print this option summary."},
  {1,"  --if0=[yes|no]"},
- {1,"       Should C code within #if 0 conditional branches be parsed [no]?"},
+ {1,"       Should code within #if 0 conditional branches be parsed [no]?"},
  {1,"  --<LANG>-alias=[+|-]aliasPattern"},
  {1,"      Add a pattern detecting a name can be used as an alternative name for LANG."},
  {1,"  --<LANG>-corpus=spec:corpusFile"},
@@ -328,6 +329,8 @@ static optionDescription LongOptionDescription [] = {
  {0,"       Should paths be relative to location of tag file [no; yes when -e]?"},
  {1,"  --totals=[yes|no]"},
  {1,"       Print statistics about source and tag files [no]."},
+ {1,"  --undef=[yes|no]"},
+ {1,"       Should #undef directives generate a macro tag [yes]?"},
  {1,"  --verbose=[yes|no]"},
  {1,"       Enable verbose messages describing actions on each source file."},
  {1,"  --version"},
@@ -2031,6 +2034,7 @@ static booleanOption BooleanOptions [] = {
 #endif
 	{ "tag-relative",   &Option.tagRelative,            TRUE    },
 	{ "totals",         &Option.printTotals,            TRUE    },
+	{ "undef",          &Option.undef,                  FALSE   },
 	{ "verbose",        &Option.verbose,                FALSE   },
 };
 

options.h

@@ -101,6 +101,7 @@ typedef struct sOptionValues {
 	stringList* etagsInclude;/* --etags-include  list of TAGS files to include*/
 	unsigned int tagFileFormat;/* --format  tag file format (level) */
 	boolean if0;            /* --if0  examine code within "#if 0" branch */
+	boolean undef;          /* --undef  generate a tag from #undef'd macros  */
 	boolean kindLong;       /* --kind-long */
 	langType language;      /* --lang specified language override */
 	boolean followLinks;    /* --link  follow symbolic links? */