================
@@ -194,3 +199,99 @@ char test_comparison_with_extent_symbol(struct incomplete
*p) {
return ((char *)p)[-1]; // no-warning
}
+// WeakLoopAssumption suppression
+///////////////////////////////////////////////////////////////////////
+
+int GlobalArray[100];
+int loop_suppress_after_zero_iterations(unsigned len) {
+ for (unsigned i = 0; i < len; i++)
+ if (GlobalArray[i] > 0)
+ return GlobalArray[i];
+ // Previously this would have produced an overflow warning because splitting
+ // the state on the loop condition introduced an execution path where the
+ // analyzer thinks that len == 0.
+ // There are very many situations where the programmer knows that an argument
+ // is positive, but this is not indicated in the source code, so we must
+ // avoid reporting errors (especially out of bounds errors) on these
+ // branches, because otherwise we'd get prohibitively many false positives.
+ return GlobalArray[len - 1]; // no-warning
+}
+
+void loop_report_in_second_iteration(int len) {
+ int buf[1] = {0};
+ for (int i = 0; i < len; i++) {
+ // When a programmer writes a loop, we may assume that they intended at
+ // least two iterations.
+ buf[i] = 1; // expected-warning{{Out of bound access to memory}}
+ }
+}
+
+void loop_suppress_in_third_iteration(int len) {
+ int buf[2] = {0};
+ for (int i = 0; i < len; i++) {
+ // We should suppress array bounds errors on the third and later iterations
+ // of loops, because sometimes programmers write a loop in sitiuations
+ // where they know that there will be at most two iterations.
+ buf[i] = 1; // no-warning
+ }
+}
+
+void loop_suppress_in_third_iteration_cast(int len) {
+ int buf[2] = {0};
+ for (int i = 0; (unsigned)(i < len); i++) {
----------------
NagyDonat wrote:
I'll check it, but I'm fairly sure that `(unsigned)0` wouldn't cause any
problems -- after all in C we don't even have a `bool` type and `0` is used as
the logical false value everywhere.
However, there are other mostly theoretical cases like `(char)256` where
stripping the cast might indeed change the value -- I'll perhaps investigate
them, but I'm not sure that it's worth to bother with writing code that covers
rare corner cases like this.
https://github.com/llvm/llvm-project/pull/109804
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