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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60
src/scripting/vm/vmexec.cpp
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@ -40,6 +40,11 @@
#include "textures/textures.h"
#include "math/cmath.h"
// This must be a separate function because the VC compiler would otherwise allocate memory on the stack for every separate instance of the exception object that may get thrown.
void ThrowAbortException(EVMAbortException reason, const char *moreinfo, ...);
// intentionally implemented in a different source file tp prevent inlining.
void ThrowVMException(VMException *x);
#define IMPLEMENT_VMEXEC
#if !defined(COMPGOTO) && defined(__GNUC__)
@ -91,7 +96,7 @@
}
#define GETADDR(a,o,x) \
if (a == NULL) { throw CVMAbortException(x, nullptr); } \
if (a == NULL) { ThrowAbortException(x, nullptr); } \
ptr = (VM_SBYTE *)a + o
static const VM_UWORD ZapTable[16] =
@ -227,57 +232,4 @@ void VMFillParams(VMValue *params, VMFrame *callee, int numparam)
}
}
void NullParam(const char *varname)
{
throw CVMAbortException(X_READ_NIL, "In function parameter %s", varname);
}
FString CVMAbortException::stacktrace;
CVMAbortException::CVMAbortException(EVMAbortException reason, const char *moreinfo, ...)
{
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(" ");
va_list ap;
va_start(ap, moreinfo);
size_t len = strlen(m_Message);
myvsnprintf(m_Message + len, MAX_ERRORTEXT - len, moreinfo, ap);
va_end(ap);
}
}