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[vm/fuzzer] Track variables to avoid inf. loops

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Rationale:
Many cases of the the loop iteration variable being modified within the
loop body, leading to infinite loops and timeouts. This patch tracks
currently active iteration variables and avoids emitting them on the lhs
of an assignment or within a pre/post operation.
Change-Id: I5e7c84f0de72410dc98d115d75b1f09e6631ece2
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/112843
Reviewed-by: Aart Bik <ajcbik@google.com>
Commit-Queue: Felicitas Hetzelt <felih@google.com>
This commit is contained in:
Felicitas Hetzelt 2019-08-13 19:39:12 +00:00 committed by commit-bot@chromium.org
parent 3cc20cd185
commit 3707f39530
1 changed files with 35 additions and 13 deletions
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48
runtime/tools/dartfuzz/dartfuzz.dart
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@ -13,7 +13,7 @@ import 'dartfuzz_api_table.dart';
// Version of DartFuzz. Increase this each time changes are made
// to preserve the property that a given version of DartFuzz yields
// the same fuzzed program for a deterministic random seed.
const String version = '1.17';
const String version = '1.18';
// Restriction on statements and expressions.
const int stmtLength = 2;
@ -40,6 +40,7 @@ class DartFuzz {
currentMethod = null;
// Setup the types.
localVars = new List<DartType>();
iterVars = new List<String>();
globalVars = fillTypes1();
globalVars.addAll(DartType.allTypes); // always one each
globalMethods = fillTypes2();
@ -208,7 +209,7 @@ class DartFuzz {
bool emitAssign() {
DartType tp = getType();
emitLn('', newline: false);
emitVar(0, tp);
emitVar(0, tp, isLhs: true);
emitAssignOp(tp);
emitExpr(0, tp);
emit(';', newline: true);
@ -282,9 +283,11 @@ class DartFuzz {
emit('; $localName$i++) {', newline: true);
indent += 2;
nest++;
iterVars.add("$localName$i");
localVars.add(DartType.INT);
emitStatements(depth + 1);
localVars.removeLast();
iterVars.removeLast();
nest--;
indent -= 2;
emitLn('}');
@ -318,9 +321,11 @@ class DartFuzz {
emitLn('while (--$localName$i > 0) {');
indent += 2;
nest++;
iterVars.add("$localName$i");
localVars.add(DartType.INT);
emitStatements(depth + 1);
localVars.removeLast();
iterVars.removeLast();
nest--;
indent -= 2;
emitLn('}');
@ -337,9 +342,11 @@ class DartFuzz {
emitLn('do {');
indent += 2;
nest++;
iterVars.add("$localName$i");
localVars.add(DartType.INT);
emitStatements(depth + 1);
localVars.removeLast();
iterVars.removeLast();
nest--;
indent -= 2;
emitLn('} while (++$localName$i < ', newline: false);
@ -642,9 +649,9 @@ class DartFuzz {
}
}
void emitScalarVar(DartType tp) {
void emitScalarVar(DartType tp, {bool isLhs = false}) {
// Collect all choices from globals, fields, locals, and parameters.
List<String> choices = new List<String>();
Set<String> choices = new Set<String>();
for (int i = 0; i < globalVars.length; i++) {
if (tp == globalVars[i]) choices.add('$varName$i');
}
@ -663,34 +670,44 @@ class DartFuzz {
if (tp == proto[i]) choices.add('$paramName$i');
}
}
// Remove possible modification of the iteration variable from the loop
// body.
if (isLhs) {
if (rand.nextInt(10) != 0) {
Set<String> cleanChoices = choices.difference(Set.from(iterVars));
if (cleanChoices.length > 0) {
choices = cleanChoices;
}
}
}
// Then pick one.
assert(choices.length > 0);
emit('${choices[rand.nextInt(choices.length)]}');
emit('${choices.elementAt(rand.nextInt(choices.length))}');
}
void emitSubscriptedVar(int depth, DartType tp) {
void emitSubscriptedVar(int depth, DartType tp, {bool isLhs = false}) {
if (tp == DartType.INT) {
emitScalarVar(DartType.INT_LIST);
emitScalarVar(DartType.INT_LIST, isLhs: isLhs);
emit('[');
emitExpr(depth + 1, DartType.INT);
emit(']');
} else if (tp == DartType.STRING) {
emitScalarVar(DartType.INT_STRING_MAP);
emitScalarVar(DartType.INT_STRING_MAP, isLhs: isLhs);
emit('[');
emitExpr(depth + 1, DartType.INT);
emit(']');
} else {
emitScalarVar(tp); // resort to scalar
emitScalarVar(tp, isLhs: isLhs); // resort to scalar
}
}
void emitVar(int depth, DartType tp) {
void emitVar(int depth, DartType tp, {bool isLhs = false}) {
switch (rand.nextInt(2)) {
case 0:
emitScalarVar(tp);
emitScalarVar(tp, isLhs: isLhs);
break;
default:
emitSubscriptedVar(depth, tp);
emitSubscriptedVar(depth, tp, isLhs: isLhs);
break;
}
}
@ -778,7 +795,7 @@ class DartFuzz {
int r = rand.nextInt(2);
emit('(');
if (r == 0) emitPreOrPostOp(tp);
emitScalarVar(tp);
emitScalarVar(tp, isLhs: true);
if (r == 1) emitPreOrPostOp(tp);
emit(')');
} else {
@ -1146,6 +1163,11 @@ class DartFuzz {
// Types of global variables.
List<DartType> globalVars;
// Names of currenty active iterator variables.
// These are tracked to avoid modifications within the loop body,
// which can lead to infinite loops.
List<String> iterVars;
// Prototypes of all global methods (first element is return type).
List<List<DartType>> globalMethods;