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<HTML><HEAD><TITLE>Section 6: All the Inform error messages</TITLE></HEAD>
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<TR><TD Valign="top"><A HREF="contents.html">Contents</A><BR><A HREF="section5.html">Back</A><BR><A HREF="chapter3.html">Forward</A><TD bgcolor="#F5DEB3"><BLOCKQUOTE><H3>6. All the Inform error messages</H3></BLOCKQUOTE><TR><TD><TD>
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Three kinds of error are reported by Inform: a fatal error is a breakdown
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severe enough to make Inform stop working at once; an error allows Inform
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to continue for the time being, but will cause Inform not to finally output
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the story file (this is to prevent damaged story files being created); and
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a warning means that Inform suspects you may have made a mistake, but will
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not take any action itself.
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<BLOCKQUOTE><H4>Fatal errors</H4></BLOCKQUOTE><P>
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<P> 1. <I> Too many errors</I>
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Too many errors: giving up
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After 100 errors, Inform stops (in case it has been given the wrong source file
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altogether, such as a program for a different language altogether).
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<P> 2. <I> Input/output problems</I>
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<P> Most commonly, Inform has the wrong filename:
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Couldn't open input file <filename>
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Couldn't open output file <filename>
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(and so on). More seriously the whole process of file input/output (or "I/O'')
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may go wrong for some reason to do with the host computer: for instance, if it
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runs out of disc space. Such errors are rare and look like this:
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I/O failure: couldn't read from temporary file 2
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Normally you can only have at most 64 files of source code in a single
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compilation. If this limit is passed, Inform generates the error
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Program contains too many source files: increase #define MAX_SOURCE_FILES
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(This might happen if the same file accidentally <TT>Include</TT>s itself.) Finally,
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if a non-existent pathname variable is set in ICL, the error
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No such path setting as <name>
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<P> 3. <I> Running out of memory</I>
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<P> If there is not enough memory even to get started,
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Run out of memory allocating <number> bytes for <something>
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Run out of memory allocating array of <number>x<number> bytes for <something>
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(There are four similar <TT>hallocate</TT> errors unique to the PC 'Quick C' port.)
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More often memory will run out in the course of compilation, like so:
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The memory setting <setting> (which is <value> at present) has been exceeded.
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Try running Inform again with $<setting>=<some-larger-number> on the command line.
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(For details of memory settings, see <A HREF="section5.html">Section 5</A> above.) In a really colossal game,
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it is just conceivable that you might hit
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One of the memory blocks has exceeded 640K
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which would need Inform to be recompiled to get around (but I do not expect
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anyone ever to have this trouble). Much more likely is the error
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The story file/module exceeds version <n> limit (<number>K) by <number> bytes
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If you're already using version 8, then the story file is full: you might be
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able to squeeze more game in using the <TT>Abbreviate</TT> directive, but basically
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you're near to the maximum game size possible. Otherwise, the error suggests
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that you might want to change the version from 5 to 8, and the game will be
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able to grow at least twice as large again.
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<BLOCKQUOTE><H4>Errors</H4></BLOCKQUOTE><P>
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There are a few conventions. Anything in double-quotes is a quotation from
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your source code; other strings are in single-quotes. The most common error
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Expected ... but found ...
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(of which there are over 100 kinds): most are straightforward to sort out,
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but a few take some practice. One of the trickiest things to diagnose is
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a loop statement having been misspelt. For example, the lines
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While (x==y) print "x is still y^";
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produce one error each:
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line 1: Error: Expected assignment or statement but found pritn
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line 2: Error: Expected ';' but found print
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The first is fine. The second is odd: a human immediately sees that
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<TT>While</TT> is meant to be a <TT>while</TT> loop, but Inform is not able to make
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textual guesses like this. Instead Inform decides that the code intended was
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While (x==y); print "x is still y^";
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with <TT>While</TT> assumed to be the name of a function which hasn't been declared yet.
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Thus, Inform thinks the mistake is that the <TT>;</TT> has been missed out.
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In that example, Inform repaired the situation and was able to carry on as normal
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in subsequent lines. But it sometimes happens that a whole cascade of errors
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is thrown up, in code which the user is fairly sure must be nearly right. What
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has happened is that one syntax mistake threw Inform off the right track, so that
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it continued not to know where it was for many lines in a row. Look at the first
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error message, fix that and then try again.
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<P> 1. <I> Reading in the source-code</I>
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Illegal character found in source: (char) <hexadecimal number>
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Unrecognised combination in source: <text>
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Alphabetic character expected after <text>
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No such accented character as <text>
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Name exceeds the maximum length of <number> characters: <name>
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The following name is reserved by Inform for its own use as a routine name;
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you can use it as a routine name yourself (to override the standard
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definition) but cannot use it for anything else: <name>
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The obsolete '#w$word' construct has been removed
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Binary number expected after '$$'
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Hexadecimal number expected after '$'
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Too much text for one pair of 's to hold
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Too much text for one pair of "s to hold
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Note that, for instance, a <TT>^</TT> character is illegal in ordinary source
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code (producing the first error above), but is allowed within quotation
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<P> 2. <I> Variables and arrays</I>
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Variable must be defined before use: <name>
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'=' applied to undeclared variable
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Local variable defined twice: <name>
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All 236 global variables already declared
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No array size or initial values given
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Array sizes must be known now, not externally defined
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An array must have a positive number of entries
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A 'string' array can have at most 256 entries
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Entries in byte arrays and strings must be known constants
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Missing ';' to end the initial array values before "[" or "]"
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The limit of 236 global variables is absolute: a program even approaching this
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limit should probably be making more use of object properties to store its
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information. "Entries... must be known constants'' is a restriction on what
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byte or string arrays may contain: basically, numbers or characters; defined
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constants (such as object names) may only be used if they have already been
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defined. This restriction does not apply to the more normally used word and
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<P> 3. <I> Routines and function calls</I>
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No 'Main' routine has been defined
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It is illegal to nest routines using '#['
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A routine can have at most 15 local variables
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Argument to system function missing
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System function given with too many arguments
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Only constants can be used as possible 'random' results
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A function may be called with at most 7 arguments
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Duplicate definition of label: <name>
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Note that the system function <TT>random</TT>, when it takes more than one
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argument, can only take constant arguments (this enables the possibilities
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to be stored efficiently within the program). Thus
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<TT>random(random(10), location)</TT> will produce an error. To make a
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random choice between non-constant values, write a <TT>switch</TT> statement instead.
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<P> 4. <I> Expressions and arithmetic</I>
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Missing operator: inserting '+'
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Evaluating this has no effect: <operator>
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'=' applied to <operator>
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Brackets mandatory to clarify order of: <operator>
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Missing operand for <operator>
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Missing operand after <something>
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Found '(' without matching ')'
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No expression between brackets '(' and ')'
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Division of constant by zero
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Label name used as value: <name>
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System function name used as value: <name>
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No such constant as <name>
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"Operators'' include not only addition <TT>+</TT>, multiplication <TT>*</TT> and so on,
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but also more exotic Inform constructs like <TT>--></TT> ("array entry'') and
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<TT>.</TT> ("property value''). An example of an operator where "Evaluating
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this has no effect'' is in the statement
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where the multiplication is a waste of time, since nothing is done with the
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result. "<I>=</I> applied to operator'' means something like
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which literally means "set $4/$<TT>fish</TT> to 7'' and results in the error
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"<I>=</I> applied to <I>/</I>''.
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"Brackets mandatory to clarify order'' means that an ambiguous expression
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frogs == ducks == geese
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requires clarification: which <TT>==</TT> is to be worked out first?
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<P> 5. <I> Miscellaneous errors in statements</I>
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'do' without matching 'until'
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'default' without matching 'switch'
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'else' without matching 'if'
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'until' without matching 'do'
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'break' can only be used in a loop or 'switch' block
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At most 32 values can be given in a single 'switch' case
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Multiple 'default' clauses defined in same 'switch'
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'default' must be the last 'switch' case
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'continue' can only be used in a loop block
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A reserved word was used as a print specification: <name>
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No lines of text given for 'box' display
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In Version 3 no status-line drawing routine can be given
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The 'style' statement cannot be used for Version 3 games
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For instance, <TT>print (fixed) X</TT> gives the "reserved word in print
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specification'' error because <TT>fixed</TT> is a reserved statement internal
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keyword. Anyway, call such a printing routine something else.
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<P> 6. <I> Object and class declarations</I>
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Two textual short names given for only one object
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The syntax '->' is only used as an alternative to 'Nearby'
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Use of '->' (or 'Nearby') clashes with giving a parent
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'->' (or 'Nearby') fails because there is no previous object
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'-> -> ...' fails because no previous object is deep enough
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Two commas ',' in a row in object/class definition
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Object/class definition finishes with ','
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Not an individual property name: <name>
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No such property name as <name>
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Not a (common) property name: <name>
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Property should be declared in 'with', not 'private': <name>
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Limit (of 32 values) exceeded for property <name>
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Duplicate-number not known at compile time
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The number of duplicates must be 1 to 10000
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Note that "common properties'' (those provided by the library,
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or those declared with <TT>Property</TT>) cannot be made <TT>private</TT>.
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All other properties are called "individual''. The "number
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of duplicates'' referred to is the number of duplicate instances
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to make for a new class, and it needs to be a number Inform can
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determine now, not later on in the source code (or in another
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module altogether). The limit 10000 is arbitrary and imposed to
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help prevent accidents.
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<P> 7. <I> Grammar</I>
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Two different verb definitions refer to <name>
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There is no previous grammar for the verb <name>
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There is no action routine called <name>
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No such grammar token as <text>
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'=' is only legal here as 'noun=Routine'
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Not an action routine: <name>
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This is a fake action, not a real one: <name>
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Too many lines of grammar for verb: increase #define MAX_LINES_PER_VERB
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At present verbs are limited to 20 grammar lines each, though this
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would be easy to increase. (A grammar of this kind of length
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can probably be written more efficiently using general parsing
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<P> 8. <I> Conditional compilation</I>
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'Ifnot' without matching 'If...'
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Second 'Ifnot' for the same 'If...' condition
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End of file reached in code 'If...'d out
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This condition can't be determined
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"Condition can't be determined'' only arises for <TT>Iftrue</TT>
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and <TT>Iffalse</TT>, which make numerical or logical tests: for instance,
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Iftrue #strings_offset==$4a50;
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can't be determined because even though both quantities are
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constants, the <TT>#strings_offset</TT> will not be known until compilation
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is finished. On the other hand, for example,
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Iftrue #version_number>5;
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can be determined, as the version number was set before compilation.
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<P> 9. <I> Miscellaneous errors in directives</I>
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You can't 'Replace' a system function already used
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Must specify 0 to 3 local variables for 'Stub' routine
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A 'Switches' directive must come before the first constant definition
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All 48 attributes already declared
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All 62 properties already declared
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'alias' incompatible with 'additive'
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The serial number must be a 6-digit date in double-quotes
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A definite value must be given as release number
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A definite value must be given as version number
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The version number must be in the range 3 to 8
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All 64 abbreviations already declared
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All abbreviations must be declared together
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It's not worth abbreviating <text>
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'Default' cannot be used in -M (Module) mode
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'LowString' cannot be used in -M (Module) mode
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<P> 10. <I> Linking and importing</I>
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File isn't a module: <name>
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Link: action name clash with <name>
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Link: program and module give differing values of <name>
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Link: module (wrongly) declared this a variable: <name>
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Link: this attribute is undeclared within module: <name>
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Link: this property is undeclared within module: <name>
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Link: this was referred to as a constant, but isn't: <name>
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Link: <type> <name> in both program and module
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Link: <name> has type <type> in program but type <type> in module
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Link: failed because too many extra global variables needed
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Link: module (wrongly) declared this a variable: <name>
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Link: this attribute is undeclared within module: <name>
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Link: this property is undeclared within module: <name>
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Link: this was referred to as a constant, but isn't: <name>
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'Import' cannot import things of this type: <name>
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'Import' can only be used in -M (Module) mode
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Note that the errors beginning "Link:'' are exactly those occurring
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during the process of linking a module into the current compilation.
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They mostly arise when the same name is used for one purpose in the
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current program, and a different one in the module.
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<P> 11. <I> Assembly language</I>
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Label out of range for branch
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Opcode specification should have form "VAR:102"
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Unknown flag: options are B (branch), S (store),
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T (text), I (indirect addressing), F** (set this Flags 2 bit)
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Only one '->' store destination can be given
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Only one '?' branch destination can be given
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No assembly instruction may have more than 8 operands
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This opcode does not use indirect addressing
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Indirect addressing can only be used on the first operand
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Store destination (the last operand) is not a variable
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Opcode unavailable in this Z-machine version: <name>
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Assembly mistake: syntax is <syntax>
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Routine contains no such label as <name>
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For this operand type, opcode number must be in range <range>
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<P> 12. <I> None of the above</I>
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<P> If you should see an incomprehensible error
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message beginning with <TT>***</TT>, then Inform itself has malfunctioned.
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This is not meant to happen, but it's conceivable that it might occur
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in the process of linking in a module which has been damaged in some way.
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Finally, error messages can also be produced from within the program
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(deliberately) using <TT>Message</TT>. It may be that a mysterious message
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is being caused by an included file written by someone other than yourself.
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<BLOCKQUOTE><H4>Warnings</H4></BLOCKQUOTE><P>
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<P> 1. <I> Questionable practices</I>
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This statement can never be reached
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There is no way that the statement being compiled can ever be executed when the
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game is played. Here is an obvious example:
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return; print "Goodbye!";
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where the <TT>print</TT> statement can never be reached, because a <TT>return</TT> must just
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have happened. Beginners often run into this example:
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"You pick up the gauntlet."; score=score+1; return;
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Here the <TT>score=score+1</TT> statement is never reached because the text, given on
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its own, means "print this, then print a new-line, then return from the current
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routine''. The intended behaviour needs something like
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print "You pick up the gauntlet.^"; score=score+1; return;
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<type> <name> declared but not used
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For example, a <TT>Global</TT> directive was used to create a variable, which was then
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never used in the program.
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'=' used as condition: '==' intended?
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if (x = 5) print "My name is Alan Partridge.";
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is legal, it's probably a mistake: <TT>x=5</TT> sets <TT>x</TT> to 5 and results in 5, so the
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condition is always true. Presumably it was a mistype for <TT>x==5</TT> meaning "test
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<TT>x</TT> to see if it's equal to 5''.
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Unlike C, Inform uses ':' to divide parts of a 'for' loop
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specification: replacing ';' with ':'
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Programmers used to the C language will now and then habitually type a <TT>for</TT>
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for (i=0; i<10; i++) ...
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but Inform needs colons, not semicolons: however, as it can see what was intended,
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it makes the correction automatically and issues only a warning.
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Missing ','? Property data seems to contain the property name <name>
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The following, part of an object declaration, is legal but unlikely:
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with found_in MarbleHall
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short_name "conch shell", name "conch" "shell",
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As written, the <TT>found_in</TT> property has a list of three values: <TT>MarbleHall</TT>,
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<TT>short_name</TT> and <TT>"conch shell"</TT>. <TT>short_name</TT> throws up the warning because
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Inform suspects that a comma was missed out and the programmer intended
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with found_in MarbleHall,
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short_name "conch shell", name "conch" "shell",
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This is not a declared Attribute: <name>
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Similarly, suppose that a game contains a <TT>pen</TT>. Then the following <TT>give</TT>
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statement is dubious but legal:
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give MarbleDoorway pen;
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The warning is caused because it's far more likely to be a misprint for
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give MarbleDoorway open;
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Without bracketing, the minus sign '-' is ambiguous
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Array Doubtful --> 50 10 -20 56;
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because Inform is not sure whether this contains three entries, the middle one
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being $10-20=-10$, or four. It guesses four, but suggests brackets to clarify
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Array entry too large for a byte
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Byte <TT>-></TT> and <TT>string</TT> arrays can only hold numbers in the range 0 to 255.
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If a larger entry is supplied, only the remainder mod 256 is stored, and this
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Verb disagrees with previous verbs: <verb>
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The <TT>Extend only</TT> directive is used to cleave off a set of synonymous English
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verbs and make them into a new Inform verb. For instance, ordinarily "take'',
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"get'', "carry'' and "hold'' are one single Inform verb, but this directive
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could split off "carry'' and "get'' from the other two. The warning would
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arise if one tried to split off "take'' and "drop'' together, which come from
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different original Inform verbs. (It's still conceivably usable, which is why
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it's a warning, not an error.)
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This does not set the final game's statusline
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An attempt to choose, e.g., <TT>Statusline time</TT> within a module, having no effect
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on the program into which the module will one day be linked. Futile.
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This module has a more advanced format than this release of the
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Inform 6 compiler knows about: it may not link in correctly
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<P> 2. <I> Obsolete usages</I>
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more modern to use 'Array', not 'Global'
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use '->' instead of 'data'
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use '->' instead of 'initial'
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use '->' instead of 'initstr'
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use 'word' as a constant dictionary address
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'#a$Act' is now superceded by '##Act'
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'#n$word' is now superceded by ''word''
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'#r$Routine' can now be written just 'Routine'
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all properties are now automatically 'long'
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use the ^ character for the apostrophe in <dictionary word>
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These all occur if Inform compiles a syntax which was correct under Inform
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5 (or earlier) but has now been withdrawn in favour of something better.
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<P><TR><TD Valign="top"><IMG SRC="icons/ddbend.gif" ALT="/\/\"><TD bgcolor="#EEEEEE"><SMALL> No Inform library file (or any other file marked <TT>System_file</TT>)
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produces warning messages. It may contain many declared but unused routines,
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or may contain obsolete usages for the sake of backward
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<HR><A HREF="contents.html">Contents</A> / <A HREF="section5.html">Back</A> / <A HREF="chapter3.html">Forward</A> <BR>
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<A HREF="chapter1.html">Chapter I</A> / <A HREF="chapter2.html">Chapter II</A> / <A HREF="chapter3.html">Chapter III</A> / <A HREF="chapter4.html">Chapter IV</A> / <A HREF="chapter5.html">Chapter V</A> / <A HREF="chapter6.html">Chapter VI</A> / <A HREF="chapterA.html">Appendix</A><HR><SMALL><I>Mechanically translated to HTML from third edition as revised 16 May 1997. Copyright © Graham Nelson 1993, 1994, 1995, 1996, 1997: all rights reserved.</I></SMALL></BODY></HTML>
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