Fix a loplugin:bufferadd false positive

(which would hit some yet-to-be-committed code)

Change-Id: I101ae4f7d00ece9d48c96764114668484b0fdd5f
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/198660
Reviewed-by: Stephan Bergmann <stephan.bergmann@collabora.com>
Tested-by: Jenkins

compilerplugins/clang/bufferadd.cxx

@@ -83,6 +83,7 @@ public:
 
     bool VisitStmt(Stmt const*);
     bool VisitCallExpr(CallExpr const*);
+    bool VisitCXXMemberCallExpr(CXXMemberCallExpr const*);
     bool VisitCXXConstructExpr(CXXConstructExpr const*);
     bool VisitUnaryOperator(UnaryOperator const*);
 
@@ -143,6 +144,35 @@ bool BufferAdd::VisitCallExpr(CallExpr const* callExpr)
     return true;
 }
 
+bool BufferAdd::VisitCXXMemberCallExpr(CXXMemberCallExpr const* expr)
+{
+    if (ignoreLocation(expr))
+    {
+        return true;
+    }
+    auto const e = dyn_cast<DeclRefExpr>(expr->getImplicitObjectArgument()->IgnoreParenImpCasts());
+    if (e == nullptr)
+    {
+        return true;
+    }
+    auto const d = dyn_cast<VarDecl>(e->getDecl());
+    if (d == nullptr)
+    {
+        return true;
+    }
+    auto const tc = loplugin::TypeCheck(d->getType());
+    if (!(tc.Class("OStringBuffer").Namespace("rtl").GlobalNamespace()
+          || tc.Class("OUStringBuffer").Namespace("rtl").GlobalNamespace()))
+    {
+        return true;
+    }
+    if (!isMethodOkToMerge(expr))
+    {
+        badMap.insert(d);
+    }
+    return true;
+}
+
 bool BufferAdd::VisitCXXConstructExpr(CXXConstructExpr const* callExpr)
 {
     if (ignoreLocation(callExpr))

compilerplugins/clang/test/bufferadd.cxx

@@ -117,6 +117,16 @@ void f7()
     OStringBuffer noelf7("xxx");
     noelf7 = "xxx" + noelf7 + "xxx";
 }
+char16_t rnd();
+void f8(sal_Int32 n)
+{
+    OUStringBuffer buf;
+    auto p = buf.appendUninitialized(n);
+    for (sal_Int32 i = 0; i != n; ++i)
+    {
+        *p++ = rnd();
+    }
+}
 }
 
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