OrdinaryMagician/vkdoom_m
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redid the exception mechanism for script-side access violations to be of more use for diagnosing problems.

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The original implementation just printed a mostly information-free message and then went on as if nothing has happened, making it ridiculously easy to write broken code and release it. Changed it to:

* Any VMAbortException will now terminate the game session and go back to the console.
* It will also print a VM stack trace with all open functions, including source file and line numbers pointing to the problem spots. For this the relevant information had to be added to the VMScriptFunction class.

An interesting effect here was that just throwing the exception object increased the VM's Exec function's stack size from 900 bytes to 70kb, because the compiler allocates a separate local buffer for every single instance of the exception object.
The obvious solution was to put this part into a subfunction so that it won't pollute the Exec function's own stack frame. Interesting side effect of this: Exec's stack requirement went down from 900 bytes to 600 bytes. This is still on the high side but already a lot better.
This commit is contained in:
Christoph Oelckers 2016-12-03 12:23:13 +01:00
commit b3783a3850
9 changed files with 231 additions and 114 deletions
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129
src/scripting/vm/vmframe.cpp
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@ -3,6 +3,7 @@
**
**---------------------------------------------------------------------------
** Copyright -2016 Randy Heit
** Copyright 2016 Christoph Oelckers
** All rights reserved.
**
** Redistribution and use in source and binary forms, with or without
@ -33,6 +34,7 @@
#include <new>
#include "dobject.h"
#include "v_text.h"
IMPLEMENT_CLASS(VMException, false, false)
IMPLEMENT_CLASS(VMFunction, true, true)
@ -48,11 +50,13 @@ VMScriptFunction::VMScriptFunction(FName name)
{
Native = false;
Name = name;
LineInfo = nullptr;
Code = NULL;
KonstD = NULL;
KonstF = NULL;
KonstS = NULL;
KonstA = NULL;
LineInfoCount = 0;
ExtraSpace = 0;
CodeSize = 0;
NumRegD = 0;
@ -82,7 +86,7 @@ VMScriptFunction::~VMScriptFunction()
}
}
void VMScriptFunction::Alloc(int numops, int numkonstd, int numkonstf, int numkonsts, int numkonsta)
void VMScriptFunction::Alloc(int numops, int numkonstd, int numkonstf, int numkonsts, int numkonsta, int numlinenumbers)
{
assert(Code == NULL);
assert(numops > 0);
@ -90,14 +94,27 @@ void VMScriptFunction::Alloc(int numops, int numkonstd, int numkonstf, int numko
assert(numkonstf >= 0 && numkonstf <= 65535);
assert(numkonsts >= 0 && numkonsts <= 65535);
assert(numkonsta >= 0 && numkonsta <= 65535);
assert(numlinenumbers >= 0 && numlinenumbers <= 65535);
void *mem = M_Malloc(numops * sizeof(VMOP) +
numkonstd * sizeof(int) +
numkonstf * sizeof(double) +
numkonsts * sizeof(FString) +
numkonsta * (sizeof(FVoidObj) + 1));
numkonsta * (sizeof(FVoidObj) + 1) +
numlinenumbers * sizeof(FStatementInfo));
Code = (VMOP *)mem;
mem = (void *)((VMOP *)mem + numops);
if (numlinenumbers > 0)
{
LineInfo = (FStatementInfo*)mem;
LineInfoCount = numlinenumbers;
mem = LineInfo + numlinenumbers;
}
else
{
LineInfo = nullptr;
LineInfoCount = 0;
}
if (numkonstd > 0)
{
KonstD = (int *)mem;
@ -190,6 +207,20 @@ int VMScriptFunction::AllocExtraStack(PType *type)
return address;
}
int VMScriptFunction::PCToLine(const VMOP *pc)
{
int PCIndex = int(pc - Code);
if (LineInfoCount == 1) return LineInfo[0].LineNumber;
for (unsigned i = 1; i < LineInfoCount; i++)
{
if (LineInfo[i].InstructionIndex > PCIndex)
{
return LineInfo[i - 1].LineNumber;
}
}
return -1;
}
//===========================================================================
//
// VMFrame :: InitRegS
@ -453,20 +484,6 @@ int VMFrameStack::Call(VMFunction *func, VMValue *params, int numparams, VMRetur
}
throw;
}
catch (CVMAbortException &exception)
{
if (allocated)
{
PopFrame();
}
if (trap != nullptr)
{
*trap = nullptr;
}
Printf("%s\n", exception.GetMessage());
return -1;
}
catch (...)
{
if (allocated)
@ -476,3 +493,83 @@ int VMFrameStack::Call(VMFunction *func, VMValue *params, int numparams, VMRetur
throw;
}
}
// Exception stuff for the VM is intentionally placed there, because having this in vmexec.cpp would subject it to inlining
// which we do not want because it increases the local stack requirements of Exec which are already too high.
FString CVMAbortException::stacktrace;
CVMAbortException::CVMAbortException(EVMAbortException reason, const char *moreinfo, va_list ap)
{
SetMessage("VM execution aborted: ");
switch (reason)
{
case X_READ_NIL:
AppendMessage("tried to read from address zero.");
break;
case X_WRITE_NIL:
AppendMessage("tried to write to address zero.");
break;
case X_TOO_MANY_TRIES:
AppendMessage("too many try-catch blocks.");
break;
case X_ARRAY_OUT_OF_BOUNDS:
AppendMessage("array access out of bounds.");
break;
case X_DIVISION_BY_ZERO:
AppendMessage("division by zero.");
break;
case X_BAD_SELF:
AppendMessage("invalid self pointer.");
break;
default:
{
size_t len = strlen(m_Message);
mysnprintf(m_Message + len, MAX_ERRORTEXT - len, "Unknown reason %d", reason);
break;
}
}
if (moreinfo != nullptr)
{
AppendMessage(" ");
size_t len = strlen(m_Message);
myvsnprintf(m_Message + len, MAX_ERRORTEXT - len, moreinfo, ap);
}
stacktrace = "";
}
// Print this only once on the first catch block.
void CVMAbortException::MaybePrintMessage()
{
auto m = GetMessage();
if (m != nullptr)
{
Printf(TEXTCOLOR_RED);
Printf("%s\n", m);
SetMessage("");
}
}
void ThrowAbortException(EVMAbortException reason, const char *moreinfo, ...)
{
va_list ap;
va_start(ap, moreinfo);
throw CVMAbortException(reason, moreinfo, ap);
va_end(ap);
}
void NullParam(const char *varname)
{
ThrowAbortException(X_READ_NIL, "In function parameter %s", varname);
}
void ThrowVMException(VMException *x)
{
throw x;
}