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Conditionalize null ptr check when casting #35100

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Merged
merged 1 commit into from
Dec 16, 2020
+20 −5
Merged

Conditionalize null ptr check when casting #35100

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25 changes: 20 additions & 5 deletions stdlib/public/runtime/DynamicCast.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -110,6 +110,12 @@ extern "C" const StructDescriptor NOMINAL_TYPE_DESCR_SYM(Sh);
/// Nominal type descriptor for Swift.String.
extern "C" const StructDescriptor NOMINAL_TYPE_DESCR_SYM(SS);

// If this returns `true`, then we will call `fatalError` when we encounter a
// null reference in a storage locaation whose type does not allow null.
static bool unexpectedNullIsFatal() {
return true; // Placeholder for an upcoming check.
}

static HeapObject * getNonNullSrcObject(OpaqueValue *srcValue,
const Metadata *srcType,
const Metadata *destType) {
Expand All @@ -120,12 +126,21 @@ static HeapObject * getNonNullSrcObject(OpaqueValue *srcValue,

std::string srcTypeName = nameForMetadata(srcType);
std::string destTypeName = nameForMetadata(destType);
swift::fatalError(/* flags = */ 0,
"Found unexpected null pointer value"
const char *msg = "Found unexpected null pointer value"
" while trying to cast value of type '%s' (%p)"
" to '%s' (%p)\n",
srcTypeName.c_str(), srcType,
destTypeName.c_str(), destType);
" to '%s' (%p)%s\n";
if (unexpectedNullIsFatal()) {
swift::fatalError(/* flags = */ 0, msg,
srcTypeName.c_str(), srcType,
destTypeName.c_str(), destType,
"");
} else {
swift::warning(/* flags = */ 0, msg,
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This might end up firing too often, if this ends up getting hit in a loop or something. I don't think you need to do this yet, but in the future this may need a flag or count to limit how many times the warning is logged in a given process.

srcTypeName.c_str(), srcType,
destTypeName.c_str(), destType,
": Continuing with null object, but expect problems later.");
}
return object;
}

/******************************************************************************/
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