[clang] [clang][StaticAnalysis] Fix an false negative bug in handling '__builtin*overflow' (PR #214553)

[Balázs Benics via cfe-commits]

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@@ -215,3 +215,12 @@ void test_add_overflow_s111(void) {
 
   clang_analyzer_warnIfReached(); // no-warning: we always get an overflow, thus choose the other branch
 }
+
+void test_add_overflow_scratch_type_too_narrow(void) {
+  int a = 32767, b = 32767;
+  signed char res;
+  
+  // This is a false negative. 32767 + 32767 == 65534, which does not
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steakhal wrote:

If this is a FN, why do we have a report?

https://github.com/llvm/llvm-project/pull/214553