ChangeLog

Symbian v0.1.	Mike Kinghan.
*	Added getopt.c and getopt.h for Standard C compatibility.
*	Added implementations for err(), errx(), warnx(), vwarnx() for
	Standard C compatibility.
*	New: Added options -v, -h
*	New: Made usage() much more explanatory.
*	New: Accept `defined x' as well as `defined (x)' as per C Standard.
*	New:
		Handle #defines and #undefs:
		We will drop a `#define sym' that reiterates a -Dsym.
		(But we can't drop `#define sym val' even if it
		reiterates -Dsym=val, because macro substitution may
		depend on it.)
		We will drop an `#undef sym' that reiterates a -Usym
		We will replace `#define sym....' with an #error
		when it contradicts -Usym or when it is a differing
		redefinition of -Dsym[=val].
		We will replace `#undef sym' with an #error when it
		contradicts -Dsym[=val]
*	New:
		Simplify truth-functional #ifs where possible even when
		they cannot be eliminated on the basis of the -D or -U assumptions,
*	Opt:
		Introduce fast comparison op_cmp() in place of frequent calls
		to strncmp() and strlen() on 1 or 2 byte strings.
*	Opt:
		The debug() function tested the debugging flag in every call
		and did nothing in case false. Replace it with function ptr
		debug that is initialised -> debug_live() when debugging == true
		and empty function debug_dummy() when debugging == false.
*	Opt:
		Eliminated numerous strlcmp() calls re-testing initial
		substrings of the same string.
*	Fix:
		Line continuations were recognised by skipcomment()
		but on reading a line continuation it did not extend
		the line buffer to get the rest of the continued line.
		So e.g.
			#define \
				FOO
		was construed as an insoluble #if followed by a plain
		line.
*	Fix: eval_table() had two early returns with LT_IF in which it failed
		to update the output argument char **cpp. This could lead
		to a line being classified LS_DIRTY - not a possible
		preprocessor line - when it was a valid preprocessor line.

Symbian v0.1.1	Mike Kinghan.
*	Fix:
		Shortcircuit evaluation of binary truth functors did not
		respect operator precedence.

Symbian v0.1.2	Mike Kinghan.
*	Fix:
		Shortcircuit evaluation of binary truth functors was
		broken in attempting to respect operator precedence.
*	Fix:
		Shortcircuit evaluation of binary truth functors
		sometimes failed to propagate the value of shortcircuited
		subexpression.
*	Fix:
		Invalid fall-through in getline() from symbol-not-found case
		to ignore-symbol case.

Symbian v0.2	Mike Kinghan
*	New:
		Substantial new logic to achieve a consistent handling of
		constants (in the absence of -k), both in cases like #if 1,
		#if 0, and in cases where constants are truth-functionally
		combined with non-constant expressions.
*	Fix:
		Previous optimisation had broken keywordedit()

Symbian v0.2.1	Mike Kinghan
*	Fix:
		#ifs of the  form p && q or p || q with q constant and p
		and p an insoluble expression where not handled correctly.
	Note:
		This version also contains inactive code preparatory to
		resolving truth-functional tautologies and contradictions
		in #ifs even where the operands are insoluable expressions.

Symbian v1.0.0	Mike Kinghan
*	New:
		Errors diagnosing conflicts between the -U or -D assumptions
		and #defines or #undefs encountered on input are now reported
		on stderr, as well as reflected by #error directives on stdout.
*	Fix:
		A missing newline at the end of a preprocessor directive at EOF
		is now reported as a non-fatal error, rather than provoking abort().

Symbian v1.0.0a	Mike Kinghan
*	Temporary hack version to enable system testing pending better handling
	for case of:
		#undef FOO
		#define FOO
	Emitted #error directives are made comments for now.

Symbian v1.0.1	Mike Kinghan
*	Fix:
		When -DFOO[=STRING] is passed we're now smart enough to treat the
		input sequence:
			#undef FOO
			#define FOO[=STRING]
		as innocuously redundant. It is deleted, rather than diagnosing
		a contradiction at #undef FOO.
Symbian v1.0.2	Mike Kinghan
*	Fix:
		When deleting a superfluous bracket, now replace it with a space
		instead of a '\v' ('\v'es being erased on output). This fixes the
		bug whereby e.g.
			# if(FOO == 0)
		becomes # ifFOO == 0
Symbian v1.0.3	Mike Kinghan
*	Fix:
		v1.0.1 introduces a bug: it is possible for a deferred #error
		diagnostic if and when it is output to overwrite the next "real"
		line of pending output, so that the #error is output twice and the
		real output line not at all. Now fixed.
	Fix:
		The fix in 1.0.1 was hastily tied off in respect of stderr output.
		The innocuous input sequence:
			#undef FOO
			#define FOO[=STRING]
		was deleted on stdout, but on stderr the #undef still provoked
		an error diagnostic, and the following #define produced another
		diagnostic to "excuse" the previous one. stderr is aligned with
		stdout out and made silent for this input sequence
	Fix:
		The fix in v1.0.2 is the undesirable side-effect of leaving
		superfluous	whitespace instead of superfluous brackets. The fix is
		now refined so that a superfluous bracket is deleted when it is
		safe to do so and otherwise replaced with a space. "Safe" means
		the superfluous bracket is flanked by whitespace or another bracket.
Symbian v1.0.4	Mike Kinghan
*	New:
		Simplification will no longer remove redundant parentheses from
		a directive if it is otherwise unchanged. In the interest of
		minimising insignificant diffs v. original code lines which are
		not __materially__ simplified will be left alone.

Symbian v1.0.5	Mike Kinghan
*	Fix:
		find_sym() was erroneously reporting a match of name1 with name2 if
		name1 was an initial substring of name2. Overlooked side-effect of
		replacing strlcmp() with strncmp().
	Fix:
		#define and #undef directives were being processed without prior
		decision as to whether the current if-state required them to be
		dropped. Thus e.g. with unifdef -UUNDEFINED -DDEFINED the sequence

			#ifdef UNDEFINED
			#undef DEFINED
			#endif

		was provoking a "contradictory #undef" diagnostic.
Symbian v1.0.6
*	New:
		If an EOF-in-comment error is given, the diagnostic now includes the
		line number at which the unclosed comment begins.
*	Fix:
		Debug output fpr #defines and #undefs was garbled.
Symbian v1.1.0	Mike Kinghan.
*	New:
		Handling of quoted strings ("<string>" or '<string>') is
		implemented. This eliminates broken behaviour when
		comment-delimiters occur within quoted strings. The implementation
		is within the function formerly known as "skipcomment()",
		which is now more suitably called "chew_on()";

		chew_on() treats paired double-quotes and paired single-quotes as
		equivalent delimiters of text within which it will not parse
		quotations of the other kind. It leaves the detection of
		single-quote strings that are illegal character constants
		to your compiler.

		chew_on() parses '\' as the escape character. A quote character that
		is preceded by an unescaped	escape is parsed as escaped, i.e. it
		does not open or close a quotation.

		chew_on() will not parse the start of a comment within quotation, but
		it will parse quotation	within a comment, and will parse the end of
		a comment within quotation within a comment. If an open quotation
		is left dangling when a containing comment closes, the quotation
		is deemed to be closed. chew_on() gives an error if an unescaped
		newline occurs within quotation	that is not within a comment.

		Thus chew_on() will never enter a an in-comment state within
		quotation, but it tolerates all	the following as comments.
		(As I cannot nest C-comments, '{{' denotes a C-comment opening
		and '}}' denotes a C-comment closure.)

			// This comment has contains an unclosed "-character.
			// This comment doesn't but it contains an unclosed single quote.
			{{ The following comment terminator isn't quoted by the
				previous apostrophe or by this "-character }}

		Unifdef now gives error if EOF is read within quotation or within
		a comment. The	diagnostic refers to the line number at which the
		dangling comment or quotation begins.
*	New:
		A new commandline option -x is introduced to control the policy for
		handling #defines or #undefs that contradict the -D or
		-U assumptions. 3 policies are provided:

			-xd		A contradictory #define or #undef is just deleted
			-xc		A diagnostic comment is inserted in place of the
					contradictory directive
			-xe		A diagnostic #error directive is inserted in place
					of the contradictory directive

		A diagnostic is written to stderr whatever the policy

*	New:
		Experimental code is removed because I have decided it has no future.
Symbian v1.1.1	Mike Kinghan.
*	New:
		The program now provides discriminating return codes. If the return
		code is negative then unifdef ended abnormally and the input was
		not completely processed. The abend codes are:

			-1	=	Commandline line usage error.
			-2	=	Some resource was exhausted, probably memory.
			-3	=	A system error stopped execution.
			-4	=	Unifdef bailed out in confusion, due to a logic bug

		If the return code is non-negative then it is a bitmask.
		If all bits are clear then the input was valid and has been copied
		to output unchanged.
		If return code & 1 is clear then the input was valid.
		If return code & 1 is set then the input was found to be in error.
		If return code & 2 is set then some input lines were deleted on
		output.
		If return code & 4 is set then #defines or #undefs in contradiction
		of the -Ds and -Uswere deleted on output.
		If return code & 8 is set then contradictory #defines or #undefs
		were replaced with diagnostic comments.
		If return code & 16 is set then contradictory #defines or #undefs
		were replaced with diagnostic #errors.

		The flagging of contradictions does not entail that the input was
		in error (return code & 1 may be clear).

		If return code & 32 is set then a parsing error was found
		(and return code & 1 is set).

		Thus unproblematic return codes are 0 and 2. Return codes that are
		odd or negative mean the output	is not valid for the CPP.

*	Fix:
		The policy flags that were supposed to be -xd, -xc and -xe were in
		fact implemented as -x0, -x1 and -x2 respectively.
		They are now as intended.

Symbian v1.1.2	Mike Kinghan
*	Fix:
		The tool distinguishes the #-line statuses LT_CONSISTENT_DEFINE_KEEP
		and LT_CONSISTENT_DEFINE_DROP, depending on whether a #define was
		non-contradictory and non-redundant vis-a-vis -Ds and -Us, or
		non-contradictory but redundant. But it neglected to make the same
		necessary distinction for #undefs. They were just distinguished as
		either contradictory or non-contradictory any non-contradictory
		was #undef was dropped.
*	New:
		The warning "output may be truncated" that was issued for any
		terminal error was unsatisfactorily vague. A new terminal error
		message gives the return code and states whether end-of-input was
		in fact reached.
*	New:
		The non-portable unix APIs err(), errx(), warnx() etc. do not well
		answer our diagnostic needs since we have started to compose
		provisional	diagnostics for deferred use, so a second family of
		diagnostic functions was introduced based on vcomplain(). This
		became messy. All diagnostic functions are now based on vcomplain()
		and the unix APIs are dispensed with.
Symbian v1.1.3	Mike Kinghan
*	Fix:
		The debug() optimisation of v0.1 introduced a bug that bites if
		debug() is called before all the commandline arguments were parsed,
		because the symbol would still be an uninitialised function pointer
		(NULL). This would occur e.g. if a -D or -U symbol was found to be
		a duplicate. The function pointer is now initialised to &debug_live.
*	Fix:
		A repercussion of parsing quotation is that we now also need to
		recognise the #error directive as initiating a sort of comment-state
		within which quotations need not be well-formed. Otherwise an #error
		directive like:

			#error You can't define FOO and BAR at the same time!

		is faulted for newline within '...

		A new chew_on()-state called ERROR_COMMENT is introduced for this
		purpose. The ERROR_COMMENT state is like the CXX_COMMENT state
		except that it is terminated by the start of a C comment as well
		as by a newline.
*	Fix:
		Innocuous logic error in chew_on() could cause an unescaped newline
		within quotation within a comment to be processed twice.
*	New:
		Shared use of static scratch buffer for assembling formatted output
		was too	fragile, and needed a static MAXLINE. Safe dynamic solution
		substituted.
Symbian v1.1.4	Mike Kinghan
*	Fix.
		Trashed the line-count in 1.1.3 :(
Symbian v1.1.5	Mike Kinghan
*	Fix:
		It was possible for chew_on() to return leaving itself
		falsely in the escape state.
	Fix:
		Recognised that text following

			#define NAME[(arg,...)]

		until an unescaped newline must be parsed in the same way as the
		text of an #error directive, i.e. as a sort of pseudo-comment that
		is indefeasibly closed by unescaped newline or by the opening of a
		true comment. Therefore have renamed the ERROR_COMMENT state
		introduced in 1.1.3 as PSEUDO_COMMENT and forced the PSEUDO_COMMENT
		state on the definiens of a #define.
	Fix:
		PSEUDO_COMMENT requires the diagnostic for EOF-within-comment to be
		generalised and that an opening line number for this disgnostic
		shall be recorded just after every #error and every
		#define NAME[(arg,...)]. The diagnostic is now:

		"EOF within comment, #error ... or #define ... context \
			commencing at line <line>"

		A line-continuation sequenence that is inadvertently not escaped
		can trigger this diagnostic for C++ comments, #errors or #defines.
	Fix:
		The strip_newline() function that I used to remove the terminal
		newline from the end of a line preparatory to quoting it in a
		diagnostic was the source of a bug when I called it before I had
		finished parsing the line. strip_newline() is now dispensed with
		in favour of more recherche but safer sprintf() formatting.
*	New:
		Now check for duplicated or contradictory -Ds and -Us while parsing
		commandline. Complain on duplicate. Bail on contradiction.
*	New:
		Complain when we output an #error directive not in #if-scope. This
		indicates either that our -D and -U assumptions conflict with
		conditions that the authors of the code wished to assert or else
		that the code was already going to #error.

		If #error was unconditional on input, say:
			"An unconditional #error directive was input".
		If #error has been made unconditional by our assumptions, say:
			"An unconditional #error directive was output".
*	New:
		Now complain of garbage following conditional directives. The
		common error "#else if..." instead of #elif" gets this diagnostic
		and is parsed as #else. The legacy behavior for garbage on
		#-lines silently discarded the current truth-state and instated
		an unresolved state.

	New:
		The new diagnostics for unconditional #error directives and
		garbage after preprocessor directive are not classified as parse
		errors - they are warning - but would be indistinguishably reported
		on stderr by the existing diagnostic machinery and not reflected
		in the return code.

		The return codes and diagnostics are now rationalised on a
		severity/reason-code model. Every diagnostic has a distinct reason
		code that also encodes a severity. 4 severities are now assigned..

		The severity of a reason code R is R & 0x1ff.

		A small number of reason codes are __summary__ reason codes,
		i.e. they belong to summary diagnostics that are written to
		stderr at termination. 4 summary reason codes are now assigned.

		All return codes are now non-negative and the return code is always
		a bitmask of severities and summary reason codes.

		The return code encodes each distinct severity and each distinct
		summary reason code that has accrued in the course of execution.
		A return code RC can be interpreted as follows:

		RC = 0:			SEVERITY_NONE
						Execution ended with 0 diagnostics.
						Good end of input reached.

		RC & 0x200:		SEVERITY_INFO
						Execution ended with at worst informational
						diagnostics.
						Good EOF reached.

		RC & 0x400:		SEVERITY_WARNING
						Execution ended with at worst warnings.
						Good EOF reached.

		RC & 0x800:		SEVERITY_ERROR
						Execution ended with at worst errors.
						Good EOF not reached.
						(Errors may be diagnosed in the commandline
						arguments or in parsing input).

		RC & 0x1000:	SEVERITY_ABEND
						Execution was aborted by an environment or internal
						error, including unavailability of resource.
						Good EOF not reached..
						(Inability to open an input file is classified as an
						abend, though it may in fact result from user error).

		RC & 0x201:		SUMMARY_DROPPED_LINES (INFO)
						Input lines were dropped on output

		RC & 0x202:		SUMMARY_CHANGED_LINES (INFO)
						Input lines were changed on output

		RC & 0x404:		SUMMARY_ERRORED_LINES (WARNING)
						Input lines were changed to #errors on output,
						because	they contradicted the -Ds or -Us.

		RC & 0x408:		SUMMARY_ERROR_OUPUT (WARNING)
						An unconditional #error was output.

		Every diagnostic written on stderr includes its reason code.
		The severity of the reason code is expressed in the diagnostic
		with the appropriate format chosen from:

			"info <reason>:"
			"warning <reason>:"
			"error <reason>:"
			"abend <reason>:"

		Reason codes are in ascending order by severity,
		i.e info < warning < error < abend.

Symbian v1.1.6	Mike Kinghan
*	Fix:
		Typo in severities enum caused contention for 1 bit flag
		in the return code. Caused exit summary to claim errors when
		there had only been info diagnostics
*	Fix:
		Corrected some errors and ommissions in usage help.

*	New:
		New commandline option -m controls verbosity. (Has no
		effect on the information in the return code.)

			-m{info|warning|error|abort}

		suppresses all diagnostics no worse than the specified
		severity.

			-msummary

		suppresses summary diagnostics at exit.

			-m0xXXXX

		suppresses all diagnostics with codes matching all bits
		in 0xXXXX

			-mverbose

		Output all diagnostics.

		If no -m specified default is -minfo -msummary (outputs
		warnings and worse, no exit summary).
*
	New:
		For readability, diagnostics now prefixed just with
		unqualified filename of executable rather than full path.

*	New:
		Exit message shorter and clearer: Either:
			"Completed [{at|before} EOF with \
				{remarks|warnings|errors}], exit code 0xXXXX"
		or
			"Aborted, exit code 0xXXX"
*	New:
		Diagnostics now refer to "foo.cpp: line nnnn:"
		rather than "foo.cpp: nnnn:"
Symbian v1.1.7	Mike Kinghan
*	Fix:
		The "Abort..." exit diagnostic lacked an argument, would
		use random memory.
*	Fix:
		The structure of the return code causes information to
		be lost on environments that truncate process return codes
		to unsigned char. (Doh!) The structure is therefore revised.
		The severity bits are shifted into the low-order four bits
		and the summary reason codes are shifted into bits immediately
		higher. The 5th-9th bits were idle in the old rc.

		Isomorphism is lost between the reason codes as given in
		diagnostics and the return code, but this is trivial.

		With this arrangement all the severity bits will be returned in
		an unsigned char to the environment, and so will all 4 summary
		bits that are currently assigned.

		Thus a return code is now interpreted:

		RC = 0:			SEVERITY_NONE

		RC & 0x1:		SEVERITY_INFO

		RC & 0x2:		SEVERITY_WARNING

		RC & 0x4:		SEVERITY_ERROR

		RC & 0x8:		SEVERITY_ABEND

		RC & 0x11:		SUMMARY_DROPPED_LINES (INFO)

		RC & 0x21:		SUMMARY_CHANGED_LINES (INFO)

		RC & 0x42:		SUMMARY_ERRORED_LINES (WARNING)

		RC & 0x82:		SUMMARY_ERROR_OUPUT (WARNING)

Symbian v1.1.8	Mike Kinghan
*	Fix:
		Serious bug caused evaluation of ...op...op... expressions or
		for op = && or op = || to stop at the first occurrence.
*	Fix:
		Shy bug would make it possible for only one of a pair of
		parentheses to be deleted in simplifying a directive,
		when the other had no flanking whitespace.
*	Fix:
		Clarified usage help for -k option.

*	Fix:
		v1.1.7 displayed its version as v1.1.6 for unifdef -v
*	Fix:
		vbail() failed to record severity in the exit code if no
		message was passed.
*	Fix:
		Superfluous occurrence of word "with" in exit message.

*	Fix:
		Reason were codes displayed with excess width.
*	New:
		The previously non-supressable exit message "Completed..."
		is now classified as an informational diagnostic, so is
		suppressed by -minfo or stronger (and so is suppressed by
		default).
*	New:
		New option -fFILE allows options to be read from FILE.
Symbian v1.2.0	Mike Kinghan
		(1.1.8 was supposed to be 1.2.0 but I forgot).
*	Fix:
		Windows build gave spurious read error on an -f file
		if the file contained newlines. The check that fread()
		returned bytes = size of file is invalid on Windows
		because the read converts CRLFs to LFs. Have relaxed
		check so that fread returns > 0.
*	Fix:
		The sequence

			#undef FOO
			#define FOO

		has been spared a "contradiction" diagnostic in the
		presence of -DFOO since 1.0.1. The diagnostic is stored
		when #undef FOO is seen but discarded if #define FOO
		turns up next. It was a bug however that the warning bit
		set in the program return code when the contradiction was
		provisionally noted was not returned to its prior set/clear
		status when the diagnostic was discarded. Thus the rc could
		indicate falsely that warnings had been issued. (Ideally
		would not set the warning bit until the diagnostic is actually
		issued but in the implementation that is more complicated
		than resetting the status quo ante).

*	New:
		-fFILE option made more flexible - is no longer exclusive
		of other commandline args:

		Can now occur anywhere in a	commandline and the options
		read from FILE will be parsed as if they occurred in the
		commandline at the position of the -f.

		This feature supports drivers that wish to input a constant
		-f file for each of variable input files. Previously was
		necessary for such a driver to assemble a fresh -f for
		each input file so that the input file would be specified
		in it. The alternative of redirecting stdin from the
		input file would cause all diagnostics to refer to "[stdin]".

		The -f option may only occur once (so it may not occur
		in the options read from an -f file).

Symbian v.1.2.1	Mike Kinghan
*	Fix:
		Blanks lines output in lieu of deleted lines when -l used
		were wrongly counted as dropped lines rather than changed lines.

*	Fix:
		Debugging literal for the PSEUDO_COMMENT state had been
		left as "#error COMMENT". Changed to "PSEUDO COMMENT"
*	Fix:
		If an input #undef was found in conflict with the
		-Ds and -Us and replaced with a diagnostic comment or #error,
		the return code would indicate lines dropped and also lines
		changed. Should only indicate lines changed. The monitoring
		of lines changed/lines dropped now simplified by just counting
		these events at the point of occurrence and then working out
		the final status bits at exit.

sunifdef v0.1.0	Mike Kinghan
*	New:
		Tool renamed sunifdef to escape unifdef compatibility.
		Root & branch modularisation of program.
*	New:
		Long options implemented. Library versions of getopt(),
		getopt_long() were non-retentrant, hampering the implementation
		of -fFILE. Using our own rentrant getopt_long(). Short
		option flags are changed to harmonise with the long option
		names.
*	New:
		Increased tolerance for sequences like:

			#undef FOO
			#define FOO

		when we have -DFOO. We now refrain from complaint if the #undef and
		the #define are separated, provided there is only whitespace and
		comments in between. We also tolerate e.g.

			#undef FOO
			#undef FOO
			#define FOO
*	New:
		Hard-coded limit on line length removed.
*	New:
		Hard-coded limit on number of symbols removed.
*	New:
		New options:
			-r | --replace
			-B | --backup [SUFFIX]
		support processing of multiple input files.

		--replace replaces each input file with the corresponding
		output file.

		--backup SUFFIX backs up each input file
		by appending SUFFIX to input filename.

		--replace changes the function of stdin when no input
		files are specified. Without --replace stdin will supply the
		sole input file, as before. With --replace, stdin will supply
		names of input files.
*	Fix:
		Parentheses that ought to be deleted failed to be deleted when
		they closed at end of line.
*	Fix:
		Modularisation compels back off the debug() optimisation
		of v0.1 because extern function ptr
		void (*debug)(const char *,...) does not honour variable
		args.

sunifdef v0.1.1	Mike Kinghan
*	New:
		Doxygen comments.
*	Fix:
		ptr_vector_insert() failed to extend heap block sufficiently on demand;
		resulted in writing past end of blocks
*	Fix:
		stderr diagnostic was not cleared from heap when --conflict delete in force,
		hence same diagnostic written repeatedly.
*	Fix:
		Spurious parse error given for `--constant eval,del' argument.
*	Fix:
		Statically initialised modules not 0-filled in optimised GCC build.
*	Fix:
		Comment-state must be set = PSEUDO_COMMENT for #error directive regardless
		of whether it is to be kept or dropped.
sunifdef v0.1.2	Mike Kinghan
*	Fix:
		The "--constant" option was wrongly written "--constants" in the usage help.
*	Fix:
		Evaluation of arithmetic comparison ops was broken.
sunifdef v0.1.3	Mike Kinghan
*	Fix:
		Pointer into line buffer within chew_on() would be invalidated if
		extend_line() reallocated the buffer.
*	Fix:
		--symbols option erroneously insisted on a --define or --undef
*	Fix:
		Did not correctly check for --symbols option to pre-empt
		symbol lookups.
sunifdef v0.1.4	Mike Kinghan
*	Fix:
		DEF0002: memmove() miscalculation could cause seg fault in symbol table lookups.
		Reported by "Juan LEON Lahoz Garcia" <juanleon1@gmail.com>
*	Fix:
		DEF0003: Faulty ordering of insertions into the symbol table could cause lookups to fail
		erroneously. Reported by "Juan LEON Lahoz Garcia" <juanleon1@gmail.com>
sunifdef v1.0	Mike Kinghan
*	New:
		REW0002: The -i | --ignore option is renamed -p | --podsym to indicate better
		that option causes lines to be treated as Plain Old data. The -t |
		--text option is renamed -P | --pod for the same reason.
*	New:
		REW0003: The implementation of the --constant policy, though
		consistent, was not conceptually coherent. Reworked.
*	New:
		FEA0006: The -p | --podsym option is honoured for `#if defined' and `#if !defined'
		directives as well as #ifdef and #ifndef
*	Fix:
		DEF0004: Overlooked occurrence of "unifdef" rather than "sunifdef" in
		diagnostic output.
*	Fix:
		DEF0005: The dropped lines count was not incremented for conflicts in
		the presence of the `--conflict delete' option
*	Fix:
		DEF0006: The SUMMARY_ERRORED_LINES status flag (return code & 64)
		was not set in respect of the `--conflict error' option.
*	Fix:
		DEF0007: The `--conflict error' option was not followed through for
		the case where it causes an unconditional #error to be output
		(return code & 128).
*	Fix:
		DEF0009: printline_cut() was capable of leaving non-printable
		house-keeping bytes in the tidied up output buffer.
*	Fix:
		DEF0010: The --constant policy should apply to constants only in
		truth-functional contexts but was applied in all contexts. In
		arithmetic contexts constants should always be treated as
		integers: the constant policy does not apply.
*	Fix:
		DEF0011: Parentheses rendered redundant by simplification
		were not deleted in all cases where they safely could be.
sunifdef v1.0.1	Mike Kinghan
*	Fix:
		DEF0012: Spit-and-polish to get a clean build with -Wall
*	Fix:
		DEF0013: Removed needless redefinition of PATH_MAX from Windows
		build.
*	Fix:
		DEF0014: `make check' always reported success even if the tests reported
		failures.
*	New:
		TST0002: The test driver test_sunifdef is strengthened:
		- 	To work without relying on system() to return a true exit code from
			the executed command
		-	To work without relaying on system() to distinguish output redirectors
			from the arguments of the command.
		-	To work in a Wine (Windows on Unix) emulator environment when the
			input pathnames are not Windified
		-	To work in a Cygwin (Unix on Windows) emulator environment when the
			input pathnames are not Windified.

sunifdef v2.0	Mike Kinghan, 2006-06-24
*	Fix:
		DEF0015: Truth-functional simplification was broken for
		constant operands when --constant eval in force.
*	Fix:
		DEF0016: Murky evaluation of the PODSYM attribute over && and ||.
		Rules now are:
		Where A and B are both evaluated:
			PODSYM(A && B) <-> PODSYM(A) && PODSYM(B)
			PODSYM(A || B) <-> PODSYM(A) || PODSYM(B)
		Where only A is evaluated by short-circuiting:
			PODSYM(A && B) <-> PODSYM(A)
			PODSYM(A || B) <-> PODSYM(A)
*	New:
		REW0001: Parser substantially simplified and much more powerful.
		Previously only evaluated truth-functions and relational operators;
		Could evaluate FOO defined -DFOO=<VAL> where only where VAL was an
		integer constant. Now can evaluate all C operators except the
		conditional operator; can evaluate FOO provided VAL can be recursively
		evaluated, but will determine that circularly defined symbol -DFOO=BAR
		-DBAR=FOO is unresolved rather loop forever.
sunifdef v2.1.	Mike Kinghan, 2006-06-27
*	Fix:
		DEF0001: All usage errors now emit a diagnosis
*	Fix:
		DEF0017: --symbols option failed to list FOO when occurring in
		#ifdef FOO or #ifndef FOO.
*	Fix:
		DEF0018: Unnecessary insistence on --replace option to process
		mutliple files with --symbols option.
*	Fix:
		DEF0019: Lingering reference to "--ignore" in usage diagnostic
		should have been changed to "--podsym".
*	Fix:
		DEF0020: The man page is more complete and correct.
*	New:
		FEA0001: Enable discarded lines to be output in the form of comments.
*	New:
		FEA0002: --symbols option now has arguments `all', `first' and
		`locate'. `all' causes all occurrences of symbols to be listed.
		`first' causes only the first occurrence of each symbol to be
		listed. `locate' causes the file name and line number to be
		appended to each listed occurrence.
*	New:
		RET0001 The --podsym option, formerly the --ignore option, is
		dropped as not being plausibly worthwhile.

*	New:	FEA0003 New --line option generates #line directives to make
		CPP line-numbering of output agree with input even of lines are
		dropped.
sunifdef v2.1.1	Mike Kinghan, 2006-07-07
*	Fix:
		DEF0021:	Evaluation of unparenthesised compound binary
		truth-functions "...op...op..." lost information of unresolved
		operands causing incorrect simplifications.
sunifdef v2.1.2	Mike Kinghan, 2006-07-16
*	Fix:
		DEF0022: Fixed warnings for 64-bit build and unused function results.
*	Fix:
		DEF0023: Fixed infrinements of C89
sunifdef v3.0 Mike Kinghan 2006-07-28
*	Fix:
		DEF0024: Usage gave -gw as default instead of -gi
*	Fix:
		DEF0025: The --symbols option could produce spurious warnings of
		contradictions.
*	Fix:
		DEF0026: The length of formatted output messages was unsafely assumed
		not to exceed 2K. Their length is now limited only by available
		heap.
*	Fix:
		DEF0027: A symbol for which --undef SYM was specified was evaluated
		as an insoluble expression. This was at odds with the C Standard,
		which stipulates the preprocessor will evaluate an undefined symbol
		as 0. The behaviour now agrees with the Standard.
*	Fix:
		DEF0028: The state of the chew module was not fully reinitialised
		at entry to each input files, causing any newline-within-quotation
		error to be spuriously repeated for subsequent input files.
*	Fix:
		DEF0029: An unarranted simplification was applied to any compound truth
		functional expression containing more than 1 operator where the
		order of evaluation was determined by prercedence rather than by
		parentheses.
*	Fix:
		REW0003: The inefficiently recursive formatting of output messaages
		is reworked.
*	New:
		REW0004: Source files diagnostic.* to report.* to reflect broader function
*	New:
		REW0005: The range of message reason codes is widened from 6 to 7 bits to
		accomodate additional diagnostics.
*	New:
		FEA0009: Unbalanced parentheses in expressions now provoke parse errors rather
		than merely causing the expression to be unresolved.
*	New:
		FEA0010: Every output message now has a reason code.
*	New:
		FEA0011: sunifdef is now agnostic between Unix and Windows line-ends.
*	New:
		FEA0012: New --recurse option enables recursion into input directories.
*	New:
		FEA0013: Progress messages are a new category of messages with a severity
		lower than informational messages.
*	New:
		FEA0014: New --filter option enables input files to be filtered by file extension.
*	New:
		FEA0015: New --keepgoing option makes sunifdef continue processing subsequent input files after errors.
*	New:
		FEA0016: Hex and octal constants are now recognised in preprocessor directives.
*	New:
		RET0002: The --gag 0xXXXX variant of --gag option is withdrawn.

sunifdef v3.1 Mike Kinghan 2007-05-06
*	New:
		FEA0017: Now can cope with multi-line C-comments embedded within
		directives.
*	New:
		RET0003: The --obfusc option is withdrawn because the contexts
		formerly classified as obfuscated are now handled in normal
		parsing.
*	Fix:
		DEF0030: -DSYM=VAL or -USYM=VAL arguments when reported by the
		--verbose option do not include the =VAL part.
*	Fix:
		DEF0031: The --constant policy should apply to constants only in
		truth-functional contexts but was applied in all contexts. In
		arithmetic contexts constants should always be treated as
		integers. (Falsely recorded as fixed DEF0010).
*	Fix:
		DEF0032: With the --file option the "Building input tree" diagnostic
		was emitted even without --verbose and could not be suppressed.
*	Fix:
		DEF0032: The --line option was not documented either in the man page
		or in the --help output.
*	Fix:
		DEF0033: Return codes expressed all severities 1 level greater than
		the true level.
*	Fix:
		DEF0034: A false verdict of differently redefined symbol
		would be returned when the definiens of the symbol was
		not itself a symbol.
*	Fix:
		DEF0035: Use of the --line option did not set the SUMMARY_CHANGED_LINES
		flag in output.

sunifdef v3.1.1 Mike Kinghan 2007-11-17
*	Fix:
		DEF0036: Failed to detect unexpected end of file within an
		unmatched #if when missing newline at end of file.
*	Fix:
		DEF0037: Summary counts of files reached and files abandoned
		would be short by 1 if a parse error was encountered without
		the --keepgoing option in force.
*	Fix:
		DEF0038: The extension-matching code supporting the --filter
		option was broken, allowing --filter EXT to match any file
		whose extension ended in EXT, even if not identical with EXT.
*	Fix:
		DEF0039: The current #if-depth and #if-line number were irrelevantly
		reported on progress messages.

sunifdef v3.1.2 Mike Kinghan 2007-11-19
*	Fix:
		DEF0040: Defective filename matching could lead to a file being
		mistaken for a directory when building the input file tree, if
		a directory name was an initial substring of a filename at the
		same level.
sunifdef v3.1.3 Mike Kinghan 2008-01-19
*	Fix:
		DEF0041: When -DSYM=VAL is specified with VAL a hex integer
		constant, rather than a decimal constant, sunifdef would
		fail to resolve SYM in expressions unless the --constant eval was
		specified, which should be unnecessary. The anomaly ocurred
		because eval_symbol() anticipated constant values only as
		decimal constants and, upon encountering a hex-prefix "0x" or
		"OX" would attempt to parse the token as an expression, invoking
		eval_table() and ultimately eval_unary(). The latter function
		_would_ resolve a hex constant, but only if --constant eval is
		in effect, since the function is assumed to operate on source
		text rather than on the definiens of -DSYM=VAL. The fix
		consists in recognising hex constants as such in eval_symbol().
*	Fix:
		DEF0042: When -DSYM=VAL is specified with VAL a soluble
		expression containing at least one integer constant operand,
		sunifdef would fail to resolve SYM in expressions unless
		--constant eval was specified. The reason is the same as in
		bug DEF0041. The fix consists in recording the origin of the
		text upon which eval_unary() is called - source text or else
		the definiens of a --defined symbol - and always resolving
		integer contstants in the latter case.
*	Fix:
		DEF0043: sunifdef did not distinguish octal numerals as integer
		constants and evaluated them as decimal numerals.
*	Fix:
		DEF0044: sunifdef did not recognise the suffixes u/U, l/L as
		belonging to integer constants. These suffixes are now
		recognised; however, sunifdef still evaluates all integer
		constants as ints and performs signed integer arithmetic upon
		them. This is unfixed bug.
*	Fix:
		DEF0045: sunifdef did not detect integer overflow in evaluating
		constants. Now detects overflow whenever the value of a constant
		will exceed INT_MAX and leaves the constant unresolved with
		a warning to that effect.

*	Fix:
		DEF0046: The --help message contained an occurrence of '--constants'
		that ought to have been '--constant'.
sunifdef v4.0.0 Koen Martens 2020-05-05
*	New:
		Forked project.
*	Fix:
		When using --kb, multi-line constructs would be replaced
		by a single blank line, and using --kc would not comment out parts
		of excluded multi-line comments.
*	Fix:
		Bug in integer overflow detection resulted in silently
		producing invalid output.
*	Fix:
		When using --kb, under certain conditions multi-line
		#elif constructions would be replaced by a single #else.

*/