[libcxx-commits] [libcxx] Reapply "[libc++] Optimize fstream::read" (PR #206453)

[Nikolas Klauser via libcxx-commits]

================
@@ -68,6 +68,25 @@ int main(int, char**) {
     test_buffer.resize(24);
     assert(std::string(test_buffer.data(), 24) == "to test buffer behaviour");
   }
+  { // Ensure that read fails gracefully with an unopened ifstream
+    // See https://llvm.org/PR168628
+    char buf[10];
+    std::ifstream ifs;
+
+    assert(!ifs.is_open());
+    assert(!ifs.bad());
+    assert(!ifs.fail());
+    assert(!ifs.eof());
+    assert(ifs.good());
+
+    ifs.read(buf, sizeof(buf));
----------------
philnik777 wrote:

I've decided to use the streambuf interface instead, since that's what this test actually cares about.

https://github.com/llvm/llvm-project/pull/206453