|
@@ -15,28 +15,41 @@ The Netherlands
|
|
|
Introduction
|
|
|
.PP
|
|
|
This document describes the implementation-specific features of the
|
|
|
-ACK Modula-2 compiler. It is not intended to teach Modula-2 programming.
|
|
|
-For a description of the Modula-2 language, the reader is referred to [1].
|
|
|
+ACK Modula-2 compiler.
|
|
|
+It is not intended to teach Modula-2 programming.
|
|
|
+For a description of the Modula-2 language,
|
|
|
+the reader is referred to [1].
|
|
|
.PP
|
|
|
The ACK Modula-2 compiler is currently available for use with the VAX,
|
|
|
-Motorola MC68020, Motorola MC68000,
|
|
|
-PDP-11, and Intel 8086 code-generators.
|
|
|
-For the 8086, MC68000, and MC68020,
|
|
|
-floating point emulation is used. This is made available with the \fI-fp\fP
|
|
|
-option, which must be passed to \fIack\fP[4,5].
|
|
|
+Motorola MC68020,
|
|
|
+Motorola MC68000,
|
|
|
+PDP-11,
|
|
|
+and Intel 8086 code-generators.
|
|
|
+For the 8086,
|
|
|
+MC68000,
|
|
|
+and MC68020,
|
|
|
+floating point emulation is used.
|
|
|
+This is made available with the \fI-fp\fP
|
|
|
+option,
|
|
|
+which must be passed to \fIack\fP[4,5].
|
|
|
.NH
|
|
|
The language implemented
|
|
|
.PP
|
|
|
This section discusses the deviations from the Modula-2 language as described
|
|
|
-in the "Report on The Programming Language Modula-2", as it appeared in [1],
|
|
|
+in the "Report on The Programming Language Modula-2",
|
|
|
+as it appeared in [1],
|
|
|
from now on referred to as "the Report".
|
|
|
-Also, the Report sometimes leaves room for interpretation. The section numbers
|
|
|
+Also,
|
|
|
+the Report sometimes leaves room for interpretation.
|
|
|
+The section numbers
|
|
|
mentioned are the section numbers of the Report.
|
|
|
.NH 2
|
|
|
Syntax (section 2)
|
|
|
.PP
|
|
|
-The syntax recognized is that of the Report, with some extensions to
|
|
|
-also recognize the syntax of an earlier definition, given in [2].
|
|
|
+The syntax recognized is that of the Report,
|
|
|
+with some extensions to
|
|
|
+also recognize the syntax of an earlier definition,
|
|
|
+given in [2].
|
|
|
Only one compilation unit per file is accepted.
|
|
|
.NH 2
|
|
|
Vocabulary and Representation (section 3)
|
|
@@ -51,8 +64,10 @@ ARRAY [0 .. 0] OF CHAR
|
|
|
.DE
|
|
|
and contains one character: \f(CW0C\fP.
|
|
|
.PP
|
|
|
-When the text of a comment starts with a '\f(CW$\fP', it may be a pragma.
|
|
|
-Currently, the following pragmas exist:
|
|
|
+When the text of a comment starts with a '\f(CW$\fP',
|
|
|
+it may be a pragma.
|
|
|
+Currently,
|
|
|
+the following pragmas exist:
|
|
|
.DS
|
|
|
.ft CW
|
|
|
(*$F (F stands for Foreign) *)
|
|
@@ -64,52 +79,81 @@ Currently, the following pragmas exist:
|
|
|
The Foreign pragma is only meaningful in a \f(CWDEFINITION MODULE\fP,
|
|
|
and indicates that this
|
|
|
\f(CWDEFINITION MODULE\fP describes an interface to a module written in another
|
|
|
-language (for instance C, Pascal, or EM).
|
|
|
+language (for instance C,
|
|
|
+Pascal,
|
|
|
+or EM).
|
|
|
Runtime checks that can be disabled are:
|
|
|
range checks,
|
|
|
\f(CWCARDINAL\fP overflow checks,
|
|
|
checks when assigning a \f(CWCARDINAL\fP to an \f(CWINTEGER\fP and vice versa,
|
|
|
and checks that \f(CWFOR\fP-loop control-variables are not changed
|
|
|
in the body of the loop.
|
|
|
-Array bound checks can be enabled, because many EM implementations do not
|
|
|
+Array bound checks can be enabled,
|
|
|
+because many EM implementations do not
|
|
|
implement the array bound checking of the EM array instructions.
|
|
|
-When enabled, the compiler generates a check before generating an
|
|
|
+When enabled,
|
|
|
+the compiler generates a check before generating an
|
|
|
EM array instruction.
|
|
|
-Even when underscores are enabled, they still may not start an identifier.
|
|
|
+Even when underscores are enabled,
|
|
|
+they still may not start an identifier.
|
|
|
.PP
|
|
|
Constants of type \f(CWLONGINT\fP are integers with a suffix letter \f(CWD\fP
|
|
|
(for instance \f(CW1987D\fP).
|
|
|
Constants of type \f(CWLONGREAL\fP have suffix \f(CWD\fP if a scale factor is missing,
|
|
|
or have \f(CWD\fP in place of \f(CWE\fP in the scale factor (f.i. \f(CW1.0D\fP,
|
|
|
\f(CW0.314D1\fP).
|
|
|
-This addition was made, because there was no way to indicate long constants,
|
|
|
+This addition was made,
|
|
|
+because there was no way to indicate long constants,
|
|
|
and also because the addition was made in Wirth's newest Modula-2 compiler.
|
|
|
.NH 2
|
|
|
Declarations and scope rules (section 4)
|
|
|
.PP
|
|
|
-Standard identifiers are considered to be predeclared, and valid in all
|
|
|
-parts of a program. They are called \fIpervasive\fP.
|
|
|
-Unfortunately, the Report does not state how this pervasiveness is accomplished.
|
|
|
-However, page 87 of [1] states: "Standard identifiers are automatically
|
|
|
-imported into all modules". Our implementation therefore allows
|
|
|
-redeclarations of standard identifiers within procedures, but not within
|
|
|
+Standard identifiers are considered to be predeclared,
|
|
|
+and valid in all
|
|
|
+parts of a program.
|
|
|
+They are called \fIpervasive\fP.
|
|
|
+Unfortunately,
|
|
|
+the Report does not state how this pervasiveness is accomplished.
|
|
|
+However,
|
|
|
+page 87 of [1] states: "Standard identifiers are automatically
|
|
|
+imported into all modules".
|
|
|
+Our implementation therefore allows
|
|
|
+redeclarations of standard identifiers within procedures,
|
|
|
+but not within
|
|
|
modules.
|
|
|
.NH 2
|
|
|
Constant expressions (section 5)
|
|
|
.PP
|
|
|
Each operand of a constant expression must be a constant:
|
|
|
-a string, a number, a set, an enumeration literal, a qualifier denoting a
|
|
|
-constant expression, a typetransfer with a constant argument, or
|
|
|
-one of the standard procedures
|
|
|
-\f(CWABS\fP, \f(CWCAP\fP, \f(CWCHR\fP, \f(CWLONG\fP, \f(CWMAX\fP, \f(CWMIN\fP,
|
|
|
-\f(CWODD\fP, \f(CWORD\fP,
|
|
|
-\f(CWSIZE\fP, \f(CWSHORT\fP, \f(CWTSIZE\fP, or \f(CWVAL\fP, with constant argument(s);
|
|
|
+a string,
|
|
|
+a number,
|
|
|
+a set,
|
|
|
+an enumeration literal,
|
|
|
+a qualifier denoting a
|
|
|
+constant expression,
|
|
|
+a type transfer with a constant argument,
|
|
|
+or one of the standard procedures
|
|
|
+\f(CWABS\fP,
|
|
|
+\f(CWCAP\fP,
|
|
|
+\f(CWCHR\fP,
|
|
|
+\f(CWLONG\fP,
|
|
|
+\f(CWMAX\fP,
|
|
|
+\f(CWMIN\fP,
|
|
|
+\f(CWODD\fP,
|
|
|
+\f(CWORD\fP,
|
|
|
+\f(CWSIZE\fP,
|
|
|
+\f(CWSHORT\fP,
|
|
|
+\f(CWTSIZE\fP,
|
|
|
+or \f(CWVAL\fP,
|
|
|
+with constant argument(s);
|
|
|
\f(CWTSIZE\fP and \f(CWSIZE\fP may also have a variable as argument.
|
|
|
.PP
|
|
|
-Floating point expressions are never evaluated compile time, because
|
|
|
-the compiler basically functions as a cross-compiler, and thus cannot
|
|
|
+Floating point expressions are never evaluated compile time,
|
|
|
+because the compiler basically functions as a cross-compiler,
|
|
|
+and thus cannot
|
|
|
use the floating point instructions of the machine on which it runs.
|
|
|
-Also, \f(CWMAX(REAL)\fP and \f(CWMIN(REAL)\fP are not allowed.
|
|
|
+Also,
|
|
|
+\f(CWMAX(REAL)\fP and \f(CWMIN(REAL)\fP are not allowed.
|
|
|
.NH 2
|
|
|
Type declarations (section 6)
|
|
|
.NH 3
|
|
@@ -117,7 +161,8 @@ Basic types (section 6.1)
|
|
|
.PP
|
|
|
The type \f(CWCHAR\fP includes the ASCII character set as a subset.
|
|
|
Values range from
|
|
|
-\f(CW0C\fP to \f(CW377C\fP, not from \f(CW0C\fP to \f(CW177C\fP.
|
|
|
+\f(CW0C\fP to \f(CW377C\fP,
|
|
|
+not from \f(CW0C\fP to \f(CW177C\fP.
|
|
|
.NH 3
|
|
|
Enumerations (section 6.2)
|
|
|
.PP
|
|
@@ -127,16 +172,22 @@ is \f(CWMAX(INTEGER)\fP.
|
|
|
Record types (section 6.5)
|
|
|
.PP
|
|
|
The syntax of variant sections in [1] is different from the one in [2].
|
|
|
-Our implementation recognizes both, giving a warning for the older one.
|
|
|
-However, see section 3.
|
|
|
+Our implementation recognizes both,
|
|
|
+giving a warning for the older one.
|
|
|
+However,
|
|
|
+see section 3.
|
|
|
.NH 3
|
|
|
Set types (section 6.6)
|
|
|
.PP
|
|
|
The only limitation imposed by the compiler is that the base type of the
|
|
|
-set must be a subrange type, an enumeration type, \f(CWCHAR\fP, or
|
|
|
-\f(CWBOOLEAN\fP.
|
|
|
-So, the lower bound may be negative.
|
|
|
-However, if a negative lower bound is used,
|
|
|
+set must be a subrange type,
|
|
|
+an enumeration type,
|
|
|
+\f(CWCHAR\fP,
|
|
|
+or \f(CWBOOLEAN\fP.
|
|
|
+So,
|
|
|
+the lower bound may be negative.
|
|
|
+However,
|
|
|
+if a negative lower bound is used,
|
|
|
the compiler gives a warning of the \fIrestricted\fP class (see the manual
|
|
|
page of the compiler).
|
|
|
.PP
|
|
@@ -173,26 +224,30 @@ or
|
|
|
(-1) + 1
|
|
|
.ft P
|
|
|
.DE
|
|
|
-I have seen some compilers that implement the first alternative, and others
|
|
|
-that implement the second. Our compiler implements the second, which is
|
|
|
-suggested by the fact that their priority is not specified, which might
|
|
|
-indicate that it is the same as that of their binary counterparts.
|
|
|
+I have seen some compilers that implement the first alternative,
|
|
|
+and others that implement the second.
|
|
|
+Our compiler implements the second,
|
|
|
+which is suggested by the fact that their priority is not specified,
|
|
|
+which might indicate that it is the same as that of their binary counterparts.
|
|
|
And then the rule about left to right decides for the second.
|
|
|
-On the other hand, one might argue that, since the grammar only allows
|
|
|
-for one unary operator in a simple expression, it must apply to the
|
|
|
-whole simple expression, not just the first term.
|
|
|
+On the other hand one might argue that,
|
|
|
+since the grammar only allows for one unary operator in a simple expression,
|
|
|
+it must apply to the whole simple expression,
|
|
|
+not just the first term.
|
|
|
.NH 2
|
|
|
Statements (section 9)
|
|
|
.NH 3
|
|
|
Assignments (section 9.1)
|
|
|
.PP
|
|
|
The Report does not define the evaluation order in an assignment.
|
|
|
-Our compiler certainly chooses an evaluation order, but it is explicitly
|
|
|
-left undefined. Therefore, programs that depend on it, may cease to
|
|
|
-work later.
|
|
|
+Our compiler certainly chooses an evaluation order,
|
|
|
+but it is explicitly left undefined.
|
|
|
+Therefore,
|
|
|
+programs that depend on it may cease to work later.
|
|
|
.PP
|
|
|
The types \f(CWINTEGER\fP and \f(CWCARDINAL\fP are assignment-compatible with
|
|
|
-\f(CWLONGINT\fP, and \f(CWREAL\fP is assignment-compatible with \f(CWLONGREAL\fP.
|
|
|
+\f(CWLONGINT\fP,
|
|
|
+and \f(CWREAL\fP is assignment-compatible with \f(CWLONGREAL\fP.
|
|
|
.NH 3
|
|
|
Case statements (section 9.5)
|
|
|
.PP
|
|
@@ -200,14 +255,17 @@ The size of the type of the case-expression must be less than or equal to
|
|
|
the word-size.
|
|
|
.PP
|
|
|
The Report does not specify what happens if the value of the case-expression
|
|
|
-does not occur as a label of any case, and there is no \f(CWELSE\fP-part.
|
|
|
-In our implementation, this results in a runtime error.
|
|
|
+does not occur as a label of any case,
|
|
|
+and there is no \f(CWELSE\fP-part.
|
|
|
+In our implementation,
|
|
|
+this results in a runtime error.
|
|
|
.NH 3
|
|
|
For statements (section 9.8)
|
|
|
.PP
|
|
|
The Report does not specify the legal types for a control variable.
|
|
|
Our implementation allows the basic types (except \f(CWREAL\fP),
|
|
|
-enumeration types, and subranges.
|
|
|
+enumeration types,
|
|
|
+and subranges.
|
|
|
A runtime warning is generated when the value of the control variable
|
|
|
is changed by the statement sequence that forms the body of the loop,
|
|
|
unless runtime checking is disabled.
|
|
@@ -219,82 +277,105 @@ Our implementation allows any result type.
|
|
|
.NH 2
|
|
|
Procedure declarations (section 10)
|
|
|
.PP
|
|
|
-Function procedures must exit through a RETURN statement, or a runtime error
|
|
|
-occurs.
|
|
|
+Function procedures must exit through a RETURN statement,
|
|
|
+or a runtime error occurs.
|
|
|
.NH 3
|
|
|
Standard procedures (section 10.2)
|
|
|
.PP
|
|
|
Our implementation supports \f(CWNEW\fP and \f(CWDISPOSE\fP
|
|
|
for backwards compatibility,
|
|
|
-but issues warnings for their use. However, see section 3.
|
|
|
+but issues warnings for their use.
|
|
|
+However,
|
|
|
+see section 3.
|
|
|
.PP
|
|
|
-Also, some new standard procedures were added, similar to the new standard
|
|
|
-procedures in Wirth's newest compiler:
|
|
|
+Also,
|
|
|
+some new standard procedures were added,
|
|
|
+similar to the new standard procedures in Wirth's newest compiler:
|
|
|
.IP \-
|
|
|
\f(CWLONG\fP converts an argument of type \f(CWINTEGER\fP or \f(CWREAL\fP to the
|
|
|
types \f(CWLONGINT\fP or \f(CWLONGREAL\fP.
|
|
|
.IP \-
|
|
|
-\f(CWSHORT\fP performs the inverse transformation, without range checks.
|
|
|
+\f(CWSHORT\fP performs the inverse transformation,
|
|
|
+without range checks.
|
|
|
.IP \-
|
|
|
-\f(CWFLOATD\fP is analogous to \f(CWFLOAT\fP, but yields a result of type
|
|
|
+\f(CWFLOATD\fP is analogous to \f(CWFLOAT\fP,
|
|
|
+but yields a result of type
|
|
|
\f(CWLONGREAL\fP.
|
|
|
.IP \-
|
|
|
-\f(CWTRUNCD\fP is analogous to \f(CWTRUNC\fP, but yields a result of type
|
|
|
+\f(CWTRUNCD\fP is analogous to \f(CWTRUNC\fP,
|
|
|
+but yields a result of type
|
|
|
\f(CWLONGINT\fP.
|
|
|
.NH 2
|
|
|
System-dependent facilities (section 12)
|
|
|
.PP
|
|
|
The type \f(CWBYTE\fP is added to the \f(CWSYSTEM\fP module.
|
|
|
It occupies a storage unit of 8 bits.
|
|
|
-\f(CWARRAY OF BYTE\fP has a similar effect to \f(CWARRAY OF WORD\fP, but is
|
|
|
-safer. In some obscure cases the \f(CWARRAY OF WORD\fP mechanism does not quite
|
|
|
+\f(CWARRAY OF BYTE\fP has a similar effect to \f(CWARRAY OF WORD\fP,
|
|
|
+but is safer.
|
|
|
+In some obscure cases the \f(CWARRAY OF WORD\fP mechanism does not quite
|
|
|
work properly.
|
|
|
.PP
|
|
|
The procedure \f(CWIOTRANSFER\fP is not implemented.
|
|
|
.NH 1
|
|
|
Backwards compatibility
|
|
|
.PP
|
|
|
-Besides recognizing the language as described in [1], the compiler recognizes
|
|
|
-most of the language described in [2], for backwards compatibility.
|
|
|
+Besides recognizing the language as described in [1],
|
|
|
+the compiler recognizes most of the language described in [2],
|
|
|
+for backwards compatibility.
|
|
|
It warns the user for old-fashioned
|
|
|
constructions (constructions that [1] does not allow).
|
|
|
-If the \fI-Rm2-3\fP option (see [6]) is passed to \fIack\fP, this backwards
|
|
|
-compatibility feature is disabled. Also, it may not be present on some
|
|
|
-smaller machines, like the PDP-11.
|
|
|
+If the \fI-Rm2-3\fP option (see [6]) is passed to \fIack\fP,
|
|
|
+this backwards compatibility feature is disabled.
|
|
|
+Also,
|
|
|
+it may not be present on some
|
|
|
+smaller machines,
|
|
|
+like the PDP-11.
|
|
|
.NH 1
|
|
|
Compile time errors
|
|
|
.PP
|
|
|
The compile time error messages are intended to be self-explanatory,
|
|
|
-and not listed here. The compiler also sometimes issues warnings,
|
|
|
+and not listed here.
|
|
|
+The compiler also sometimes issues warnings,
|
|
|
recognizable by a warning-classification between parentheses.
|
|
|
-Currently, there are 3 classifications:
|
|
|
+Currently,
|
|
|
+there are 3 classifications:
|
|
|
.IP "(old-fashioned use)"
|
|
|
.br
|
|
|
-These warnings are given on constructions that are not allowed by [1], but are
|
|
|
-allowed by [2].
|
|
|
+These warnings are given on constructions that are not allowed by [1],
|
|
|
+but are allowed by [2].
|
|
|
.IP (strict)
|
|
|
.br
|
|
|
-These warnings are given on constructions that are supported by the
|
|
|
-ACK Modula-2 compiler, but might not be supported by others.
|
|
|
-Examples: functions returning structured types, SET types of subranges with
|
|
|
+These warnings are given on constructions that are supported by the
|
|
|
+ACK Modula-2 compiler,
|
|
|
+but might not be supported by others.
|
|
|
+Examples: functions returning structured types,
|
|
|
+SET types of subranges with
|
|
|
negative lower bound.
|
|
|
.IP (warning)
|
|
|
.br
|
|
|
-The other warnings, such as warnings about variables that are never assigned,
|
|
|
-never used, etc.
|
|
|
+The other warnings,
|
|
|
+such as warnings about variables that are never assigned,
|
|
|
+never used,
|
|
|
+etc.
|
|
|
.NH 1
|
|
|
Runtime errors
|
|
|
.PP
|
|
|
The ACK Modula-2 compiler produces code for an EM machine as defined in [3].
|
|
|
-Therefore, it depends on the implementation
|
|
|
+Therefore,
|
|
|
+it depends on the implementation
|
|
|
of the EM machine for detection some of the runtime errors that could occur.
|
|
|
.PP
|
|
|
The \fITraps\fP module enables the user to install his own runtime
|
|
|
error handler.
|
|
|
The default one just displays what happened and exits.
|
|
|
-Basically, a trap handler is just a procedure that takes an INTEGER as
|
|
|
-parameter. The INTEGER is the trap number. This INTEGER can be one of the
|
|
|
-EM trap numbers, listed in [3], or one of the numbers listed in the
|
|
|
+Basically,
|
|
|
+a trap handler is just a procedure that takes an INTEGER as
|
|
|
+parameter.
|
|
|
+The INTEGER is the trap number.
|
|
|
+This INTEGER can be one of the
|
|
|
+EM trap numbers,
|
|
|
+listed in [3],
|
|
|
+or one of the numbers listed in the
|
|
|
\fITraps\fP definition module.
|
|
|
.PP
|
|
|
The following runtime errors may occur:
|
|
@@ -303,7 +384,8 @@ The following runtime errors may occur:
|
|
|
The detection of this error depends on the EM implementation.
|
|
|
.IP "range bound error"
|
|
|
.br
|
|
|
-Range bound errors are always detected, unless runtime checks are disabled.
|
|
|
+Range bound errors are always detected,
|
|
|
+unless runtime checks are disabled.
|
|
|
.IP "set bound error"
|
|
|
.br
|
|
|
The detection of this error depends on the EM implementation.
|
|
@@ -313,10 +395,12 @@ The current implementations detect this error.
|
|
|
The detection of this error depends on the EM implementation.
|
|
|
.IP "cardinal overflow"
|
|
|
.br
|
|
|
-This error is detected, unless runtime checks are disabled.
|
|
|
+This error is detected,
|
|
|
+unless runtime checks are disabled.
|
|
|
.IP "cardinal underflow"
|
|
|
.br
|
|
|
-This error is detected, unless runtime checks are disabled.
|
|
|
+This error is detected,
|
|
|
+unless runtime checks are disabled.
|
|
|
.IP "real overflow"
|
|
|
.br
|
|
|
The detection of this error depends on the EM implementation.
|
|
@@ -339,9 +423,10 @@ The detection of this error depends on the EM implementation.
|
|
|
.br
|
|
|
This error occurs when assigning a negative value of type INTEGER to a
|
|
|
variable of type CARDINAL,
|
|
|
-or when assigning a value of CARDINAL, that is > MAX(INTEGER), to a
|
|
|
-variable of type INTEGER.
|
|
|
-It is detected, unless runtime checking is disabled.
|
|
|
+or when assigning a value of CARDINAL that is > MAX(INTEGER),
|
|
|
+to a variable of type INTEGER.
|
|
|
+It is detected,
|
|
|
+unless runtime checking is disabled.
|
|
|
.IP "stack overflow"
|
|
|
.br
|
|
|
The detection of this error depends on the EM implementation.
|
|
@@ -358,17 +443,22 @@ All current EM implementations detect this error.
|
|
|
.IP "stack size of process too large"
|
|
|
.br
|
|
|
This is most likely to happen if the reserved space for a coroutine stack
|
|
|
-is too small. In this case, increase the size of the area given to
|
|
|
-\fCWNEWPROCESS\fP. It can also happen if the stack needed for the main
|
|
|
-process is too large and there are coroutines. In this case, the only fix is
|
|
|
-to reduce the stack size needed by the main process, f.i. by avoiding local
|
|
|
-arrays.
|
|
|
+is too small.
|
|
|
+In this case,
|
|
|
+increase the size of the area given to
|
|
|
+\f(CWNEWPROCESS\fP.
|
|
|
+It can also happen if the stack needed for the main
|
|
|
+process is too large and there are coroutines.
|
|
|
+In this case,
|
|
|
+the only fix is to reduce the stack size needed by the main process,
|
|
|
+f.i. by avoiding local arrays.
|
|
|
.IP "too many nested traps + handlers"
|
|
|
.br
|
|
|
This error can only occur when the user has installed his own trap handler.
|
|
|
It means that during execution of the trap handler another trap has occurred,
|
|
|
and that several times.
|
|
|
-In some cases, this is an error because of overflow of some internal tables.
|
|
|
+In some cases,
|
|
|
+this is an error because of overflow of some internal tables.
|
|
|
.IP "no RETURN from function procedure"
|
|
|
.br
|
|
|
This error occurs when a function procedure does not return properly
|
|
@@ -378,35 +468,53 @@ This error occurs when a function procedure does not return properly
|
|
|
This error might occur when you use floating point operations on an
|
|
|
implementation that does not have floating point.
|
|
|
.PP
|
|
|
-In addition, some of the library modules may give error messages.
|
|
|
+In addition,
|
|
|
+some of the library modules may give error messages.
|
|
|
The \fBTraps\fP-module has a suitable mechanism for this.
|
|
|
.NH 1
|
|
|
Calling the compiler
|
|
|
.PP
|
|
|
See [4,5,6] for a detailed explanation.
|
|
|
.PP
|
|
|
-Ths compiler itself has no version checking mechanism. A special linker
|
|
|
-would be needed to do that. Therefore, a makefile generator is included [7].
|
|
|
+The compiler itself has no version checking mechanism.
|
|
|
+A special linker
|
|
|
+would be needed to do that.
|
|
|
+Therefore,
|
|
|
+a makefile generator is included [7].
|
|
|
.NH 1
|
|
|
The procedure call interface
|
|
|
.PP
|
|
|
-Parameters are pushed on the stack in reversed order, so that the EM AB
|
|
|
+Parameters are pushed on the stack in reversed order,
|
|
|
+so that the EM AB
|
|
|
(argument base) register indicates the first parameter.
|
|
|
-For VAR parameters, its address is passed, for value parameters its value.
|
|
|
+For VAR parameters,
|
|
|
+its address is passed,
|
|
|
+for value parameters its value.
|
|
|
The only exception to this rule is with conformant arrays.
|
|
|
-For conformant arrays, the address is passed, and an array descriptor is
|
|
|
-passed. The descriptor is an EM array descriptor. It consists of three
|
|
|
-fields: the lower bound (always 0), upper bound - lower bound, and the
|
|
|
-size of the elements.
|
|
|
+For conformant arrays,
|
|
|
+the address is passed,
|
|
|
+and an array descriptor is
|
|
|
+passed.
|
|
|
+The descriptor is an EM array descriptor.
|
|
|
+It consists of three
|
|
|
+fields: the lower bound (always 0),
|
|
|
+upper bound - lower bound,
|
|
|
+and the size of the elements.
|
|
|
The descriptor is pushed first.
|
|
|
-If the parameter is a value parameter, the called routine must make sure
|
|
|
-that its value is never changed, for instance by making its own copy
|
|
|
-of the array. The Modula-2 compiler does exactly this.
|
|
|
+If the parameter is a value parameter,
|
|
|
+the called routine must make sure
|
|
|
+that its value is never changed,
|
|
|
+for instance by making its own copy
|
|
|
+of the array.
|
|
|
+The Modula-2 compiler does exactly this.
|
|
|
.PP
|
|
|
When the size of the return value of a function procedure is larger than
|
|
|
-the maximum of \fCWSIZE(LONGREAL)\fP and twice the pointer-size, the caller
|
|
|
-reserves this space on the stack, above the parameters. Callee then stores
|
|
|
-its result there, and returns no other value.
|
|
|
+the maximum of \f(CWSIZE(LONGREAL)\fP and twice the pointer-size,
|
|
|
+the caller reserves this space on the stack,
|
|
|
+above the parameters.
|
|
|
+Callee then stores
|
|
|
+its result there,
|
|
|
+and returns no other value.
|
|
|
.NH 1
|
|
|
References
|
|
|
.IP [1]
|