281 lines
14 KiB
Plaintext
281 lines
14 KiB
Plaintext
.\" List of all warnings; source of warn_msg and warn.h
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.\"
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.\" $Id$
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.\"
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.\" This file contains the warnings issued by the interpreter, together
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.\" with their names and values in the code of the interpreter. Some of
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.\" the source files of the interpreter are generated from the Wn
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.\" macros in this file.
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.\" When modifying this file, preserve the parameters of the Wn macros.
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.de Wn \" <text> <define> <value>
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.IP \\$3. 7
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.B "\\$1"
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.br
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.. Wn
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.bp
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.DS C
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APPENDIX A
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.DE
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.SH
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List of Warnings.
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.PP
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The shadow-byte administration makes it possible to check for a
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wide range of errors during run-time.
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We have tried to make the diagnostics self-explanatory and especially useful
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for the C-programmer.
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The warnings are printed in the message file, together with source file
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and line number.
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The complete list of warnings is presented here, followed by an
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explanation of what might be wrong.
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Often, these explanations implicitly assume that the program
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being interpreted, was originally written in C (and not Pascal, Basic etc.).
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.LP
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.I "Reading the load file"
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.Wn "Floating point instructions flag in header ignored" WFLUSED 1
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.Wn "No float initialisation in this version" WFLINIT 2
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The interpreter was compiled with the NOFLOAT option; code involving
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floating point operations can be run as long as the actual
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instructions are avoided.
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.Wn "Extra-test flag in header ignored" WEXTRIGN 4
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The interpreter already tests anything conceivable.
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.Wn "Maximum line number in header was 0" WNLINEZR 5
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This number could be used to allocate tables for tallying; these tables are,
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however, expanded as needed, so the number is immaterial.
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.Wn "Bad float initialisation" WBADFLOAT 7
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The loadfile contains a floating point denotation which does not
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satisfy the syntax (see 2.6).
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Examining the loadfile (with \fBod \-c\fP) might show the syntax error.
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Probably there is a bug in the front-end, creating floats with
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a bad syntax.
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.LP
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.I "System calls"
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.Wn "IOCTL \- bad or unimplemented request" WBADIOCTL 11
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The second parameter to the ioctl() request (the operation code) is invalid or
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not implemented; since there are many different opcodes on the various UNIX
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systems, it is difficult to tell which. The system call fails.
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.Wn "MPXCALL \- not (yet) implemented" WMPXIMP 14
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.Wn "PROFIL \- not (yet) implemented" WPROFILIMP 15
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.Wn "PTRACE \- not (yet) implemented" WPTRACEIMP 16
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The monitor calls \fImpxcall()\fP, \fIprofil()\fP and \fIptrace()\fP
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have not been implemented. The monitor call fails.
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.Wn "Inaccessible memory in system call" WMONFLT 21
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Bad pointers passed to system calls do not cause a memory fault (which in UNIX
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would happen to the kernel), but cause the system call to fail with the UNIX
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variable errno set to 14 (EFAULT). It seems likely that the program is at
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fault, but there is also a good possibility that a library routine made
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unwarranted assumptions about word size and pointer size.
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.Wn "READ \- buffer resides in unallocated memory" WRUMEM 23
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.Wn "READ \- buffer across global data area and heap" WRGDAH 24
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When the buffer passed to the read() system call is situated (completely
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or partially) in unallocated memory (beyond \fIHP\fP) or begins
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in the global data area and ends in the heap, the appropriate warning
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is given.
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The buffer is not written.
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.Wn "WRITE \- buffer resides in unallocated memory" WWUMEM 25
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.Wn "WRITE \- buffer across global data area and heap" WWGDAH 26
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.Wn "WRITE \- (part of) global buffer is undefined" WWGUNDEF 27
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.Wn "WRITE \- (part of) local buffer is undefined" WWLUNDEF 28
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The first two are equivalent to the READ-errors above.
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Writing out a buffer usually makes no sense when the contents are undefined,
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so one of the latter two warnings will be generated in this case.
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A global buffer resides in the data partition; a local buffer resides in
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the stack partition.
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This corresponds to global and local variables in a C-program.
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In the first two cases the WRITE is not performed, in the latter two cases
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it is.
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.LP
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.I "Traps and signals"
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.Wn "SIGTRP \- bad signo argument" WILLSN 31
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The \fIsigtrp()\fP monitor call allows \fIsig_no\fP arguments in the
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range [1..17] (UNIX Version 7 signals); the actual argument is out of range.
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.Wn "SIGTRP \- signo argument is a synchronous trap" WUNIXTR 32
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The signal is one that can only be caused synchronously by the running program
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on UNIX; it cannot occur to an interpreted program.
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.Wn "SIGTRP \- bad trapno argument" WILLTN 33
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The \fIsigtrp()\fP monitor call allows \fItrap_no\fP arguments between 0 and
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252, and the special values \-2 and \-3; the actual argument is not one of
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these.
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.Wn "Heap overflow due to command line limitation" WEHEAP 36
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.Wn "Stack overflow due to command line limitation" WESTACK 37
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The maximum sizes of the heap and the stack can be limited by options on the
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command line. If overflow occurs due to such limitations, the corresponding
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trap is taken, preceded by one of the above warnings. If the memory of the
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interpreter itself is exhausted, a fatal error follows.
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.LP
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.I "Run-time type checking"
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.Wn "Local character expected" WLCEXP 41
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.Wn "Global character expected" WGCEXP 42
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.Wn "Local integer expected" WLIEXP 43
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.Wn "Global integer expected" WGIEXP 44
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.Wn "Local float expected" WLFEXP 45
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.Wn "Global float expected" WGFEXP 46
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.Wn "Local data pointer expected" WLDPEXP 47
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.Wn "Global data pointer expected" WGDPEXP 48
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.Wn "Local instruction pointer expected" WLIPEXP 49
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.Wn "Global instruction pointer expected" WGIPEXP 50
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In general, a type violation has taken place when one of
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these warnings is given.
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The \fBfloat\fP- and \fBinstruction pointer\fP warnings are rare and will
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usually be easy traceable.
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\fBInteger/character expected\fP will normally occur when unsigned arithmetic
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is performed on datapointers or when memory containing objects other than
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integers is copied bytewise.
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Often, this warning is followed by a warning \fBdatapointer expected\fP.
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This is due to our decision of transforming pointers to (unsigned) integers
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after doing unsigned arithmetic on them.
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When such a transformed integer is dereferenced (as if it were a pointer)
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or, in general, when it is treated as a pointer, this results in a warning.
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The present library implementation of malloc() causes such a
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sequence of errors.
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.LP
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These messages are always followed by a tentative description of what is found
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in memory at the offending place.
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.Wn "Actual memory is undefined" WWASUND 61
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.Wn "Actual memory contains an integer" WWASINT 62
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.Wn "Actual memory contains a float" WWASFLOAT 63
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.Wn "Actual memory contains a data pointer" WWASDATAP 64
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.Wn "Actual memory contains an instruction pointer" WWASINSP 65
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.Wn "Actual memory contains mixed information" WWASMISC 66
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If the contents of the area was undefined,
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check the source code for an uninitialized variable of the mentioned type.
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Officially, the use of an undefined value
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should result in a EIUND or EFUND trap but the occurrence is
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so common that a warning is more appropriate.
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The contents of memory are described as mixed if the data consists of pieces
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of different types. This happens, e.g., when caller and callee do not agree on
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the types and lengths of the parameters.
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.LP
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.I "Protection"
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.br
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.Wn "Destroying contents of ROM (at or near loc 0)" WDESROM 71
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The program stores a value in Read-Only Memory; the only ROM in the present
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implementation is the area near location 0. The warning probably results from
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storing under a NULL pointer. This is only a warning, the store operation is
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executed normally. Reads from location 0 are not detected.
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.Wn "Destroying contents of Return Status Block" WDESRSB 72
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The Return Status Block is the stack area containing the return address, the
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dynamic link, etc.
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This may or may not be an error.
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The current implementation of \fIsetjmp()\fP/\fIlongjmp()\fP
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may be responsible for it.
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If the program does not use setjmp(), there \fIis\fP something
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very wrong (e.g. argument for ASP too large).
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Note that there are some library routines (such as \fIalarm()\fP) which
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use \fIsetjmp()\fP.
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.Wn "Logical operation using undefined operand(s)" WUNLOG 81
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.Wn "Comparing undefined operand(s)" WUNCMP 82
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The logical operations AND, XOR, IOR, COM and the compare operation
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CMS do their jobs bytewise.
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If one of the bytes is found to be undefined, the corresponding warning
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is given, and the operation is stopped immediately.
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The stack is adjusted so interpretation may continue.
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.br
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It is hard to say what went wrong.
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Possibly, the argument of the instruction at hand (which indicates the
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size of the objects to be compared), was too large.
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.LP
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.I "Bad operands"
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.Wn "Shift over negative distance" WSHNEG 91
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.Wn "Shift over too large distance" WSHLARGE 92
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Shift instructions yield undefined results if the shift distance is negative
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or larger than the object size.
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.Wn "Pointer arithmetic yields pointer to bad segment" WSEGADP 93
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When doing pointer arithmetic (ADP, ADS), the operand and result pointer
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must be in the same \fIsegment\fP (see sec. 4).
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E.g. loading the address of the first local and adding 20 to it will
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certainly give this warning.
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.Wn "Subtracting pointers to different segments" WSEGSBS 94
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Pointers may be subtracted only if they point into the same segment.
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.Wn "Pointer arithmetic with NULL pointer" WNULLPA 96
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By definition it is illegal to do arithmetic with null pointers.
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Integers with the size of a pointer and the value zero are recognized
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as NULL pointers.
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A well-known C-trick to compute the offset of some field in a struct
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is converting the null-pointer to the type of the struct and simply
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taking the address of the field.
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This trick will \-when translated and interpreted\- generate this warning
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because it results in arithmetic with the NULL pointer.
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.LP
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.I "Return area"
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.Wn "Returned function result too large" WRFUNLAR 101
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.Wn "Returned function result too small" WRFUNSML 102
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This warning is generated when the size of the expected return value
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is not equal to the size actually returned.
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.br
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An interpreted program may have fallen through the end of
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the code without explicitly doing an \fIexit()\fP or \fIreturn()\fP.
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The start-up routine (\fIcrt0()\fP) however always expects to get some
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value returned by the program proper.
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.br
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Another (less probable) possibility of course is that the code contains
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a subroutine or function call that does not return properly (e.g.
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it returns a short instead of a long).
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.Wn "Returned function result may be garbled" WRFUNGAR 103
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This warning will be generated, when the contents of the FRA are fetched
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after some instruction is executed which can mess up the area.
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Compiler-generated loadfiles should not generate this message.
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.LP
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.I "Return Status Block"
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.Wn "RET did not find a Return Status Block" WRETBAD 111
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.Wn "Used RET to return from a trap" WRETTRAP 112
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The RET instruction found a garbled Return Status Block, or on that resulted
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from a trap.
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.Wn "RTT did not find a Return Status Block" WRTTBAD 115
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.Wn "RTT on empty stack" WRTTEMPTY 116
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.Wn "Used RTT to return from a call" WRTTCALL 117
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.Wn "Used RTT to return from a non-returnable trap" WRTTNRTT 118
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The RTT (Return from Trap) instruction found a Return Status block that was not
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created properly by a trap.
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.Wn "Stack Pointer too large in RET" WRETSTL 121
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.Wn "Stack Pointer too small in RET" WRETSTS 122
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.Wn "Stack Pointer too large in RTT" WRTTSTL 125
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.Wn "Stack Pointer too small in RTT" WRTTSTS 126
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According to the EM Manual (4.2), "the value of SP just after the return
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value has been popped must be the same as the
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value of SP just before executing the first instruction of the
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invocation."
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If the Stack Pointer is too large, some dynamically allocated item or some
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temporary result may have been left behind on the stack.
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If the Stack Pointer is too small, some locals have been unstacked.
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Since the interpreter has enough information in the Return Status Block, it
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recovers correctly from these errors.
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.LP
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.I "Traps"
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.LP
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Some traps have ambiguous or non-obvious causes.
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As far as possible, these are preceded by a warning, explaining the
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circumstances of the trap.
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.Wn "Trap ESTACK: DCH on bad LB" WDCHBADLB 131
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.Wn "Trap ESTACK: LPB on bad LB" WLPBBADLB 132
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.Wn "Trap ESTACK: SP retracted over Return Status Block" WSPGTLB 133
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.Wn "Trap ESTACK: SP moved into data area" WSPINHEAP 134
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.Wn "Trap ESTACK: SP set to non-word-boundary" WSPODD 135
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.Wn "Trap ESTACK: LB set out of stack" WLBOUT 136
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.Wn "Trap ESTACK: LB set to non-word-boundary" WLBODD 137
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.Wn "Trap ESTACK: LB set to position where there is no RSB" WLBRSB 138
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.Wn "Trap EHEAP: HP retracted into Global Data Area" WHPGDA 141
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.Wn "Trap EHEAP: HP pushed into stack" WHPSTACK 142
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.Wn "Trap EHEAP: HP set to non-word-boundary" WHPODD 143
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.Wn "Trap EILLINS: unknown opcode" WBADOPC 151
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.Wn "Trap EILLINS: conversion with unacceptable size for this machine" WILLCONV 152
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.Wn "Trap EILLINS: FIL with non-existing address" WILLFIL 153
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.Wn "Trap EILLINS: LFR with too large size" WILLLFR 154
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.Wn "Trap EILLINS: RET with too large size" WILLRET 155
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.Wn "Trap EILLINS: instruction argument of class c does not fit a word" WARGC 156
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.Wn "Trap EILLINS: instruction on double word on machine with word size 4" WARGD 157
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.Wn "Trap EILLINS: local offset too large" WARGL 158
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.Wn "Trap EILLINS: instruction argument of class g not in GDA" WARGG 159
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.Wn "Trap EILLINS: fragment offset too large" WARGF 160
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.Wn "Trap EILLINS: counter in lexical instruction out of range" WARGN 161
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.Wn "Trap EILLINS: non-existent procedure identifier" WARGP 162
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.Wn "Trap EILLINS: illegal register number" WARGR 163
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.Wn "Trap EBADPC: jump out of text segment" WPCOVFL 172
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.Wn "Trap EBADPC: jump out of procedure fragment" WPCPROC 173
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.Wn "Trap EBADGTO: GTO does not restore an existing RSB" WGTORSB 181
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.Wn "Trap EBADGTO: GTO descriptor on the stack" WGTOSTACK 182
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.Wn "Trap caused by TRP instruction" WTRP 191
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.ig
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.Wn "Last warning" WMSG 199
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!Leave these lines here!
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..
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