[clang] [clang][analyzer] Support strlen with offset to string literal in CStringChecker (PR #159795)

[Balázs Kéri via cfe-commits]

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@@ -235,6 +242,19 @@ void testStrlenCallee(void) {
   clang_analyzer_eval(lenBefore == lenAfter); // expected-warning{{UNKNOWN}}
 }
 
+void strlen_symbolic_offset(unsigned x) {
+  const char *str = "abcd";
+  if (x > 3)
+    return;
+  // FIXME: these should be known
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balazske wrote:

The test was about the limits of the range for `strlen(str + x)` (but somehow conditions were wrong). Still this range is not recognized by the analyzer (probably because there is a subtraction).

https://github.com/llvm/llvm-project/pull/159795