[clang] [clang][analyzer] fix false positive of BlockInCriticalSectionChecker (PR #126752)

[Gábor Horváth via cfe-commits]

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@@ -0,0 +1,49 @@
+// RUN: %clang_analyze_cc1 \
+// RUN:   -analyzer-checker=unix.BlockInCriticalSection \
+// RUN:   -std=c++11 \
+// RUN:   -analyzer-output text \
+// RUN:   -verify %s
+
+// expected-no-diagnostics
+
+namespace std {
+  struct mutex {
+    void lock() {}
+    void unlock() {}
+  };
+  template<typename T>
+  struct lock_guard {
+    lock_guard<T>(std::mutex) {}
+    ~lock_guard<T>() {}
+  };
+  template<typename T>
+  struct unique_lock {
+    unique_lock<T>(std::mutex) {}
+    ~unique_lock<T>() {}
+  };
+  template<typename T>
+  struct not_real_lock {
+    not_real_lock<T>(std::mutex) {}
+  };
+  } // namespace std
+
+std::mutex mtx;
+using ssize_t = long long;
+using size_t = unsigned long long;
+int open (const char *__file, int __oflag, ...);
+ssize_t read(int fd, void *buf, size_t count);
+void close(int fd);
+#define O_RDONLY	     00
+# define O_NONBLOCK	  04000
+
+void foo()
+{
+    std::lock_guard<std::mutex> lock(mtx);
+
+    const char *filename = "example.txt";
+    int fd = open(filename, O_RDONLY | O_NONBLOCK);
+
+    char buffer[200] = {};
+    read(fd, buffer, 199); // no-warning: fd is a non-block file descriptor
+    close(fd);
+}
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Xazax-hun wrote:

Nit: missing new line at the end of the file. 

https://github.com/llvm/llvm-project/pull/126752