[clang] [analyzer] Avoid unnecessary super region invalidation in `CStringChecker` (PR #146212)

[Donát Nagy via cfe-commits]

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@@ -2223,16 +2223,81 @@ void CStringChecker::evalStrcpyCommon(CheckerContext &C, const CallEvent &Call,
         Result = lastElement;
     }
 
+    // For bounded method, amountCopied take the minimum of two values,
+    // for ConcatFnKind::strlcat:
+    // amountCopied = min (size - dstLen - 1 , srcLen)
+    // for others:
+    // amountCopied = min (srcLen, size)
+    // So even if we don't know about amountCopied, as long as one of them will
+    // not cause an out-of-bound access, the whole function's operation will not
+    // too, that will avoid invalidating the superRegion of data member in that
+    // situation.
+    bool CouldAccessOutOfBound = true;
+    if (IsBounded && amountCopied.isUnknown()) {
+      // Get the max number of characters to copy.
+      SizeArgExpr lenExpr = {{Call.getArgExpr(2), 2}};
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NagyDonat wrote:

As far as I see you only use the `.Expression` member of this object -- just declare `const Expr *LenExpr = Call.getArgExpr(2)` instead of this.

https://github.com/llvm/llvm-project/pull/146212