[clang] [clang][analyzer] Add C standard streams to the internal memory space (PR #147766)

[Balazs Benics via cfe-commits]

=?utf-8?q?Balázs_Kéri?= <balazs.keri at ericsson.com>
Message-ID:
In-Reply-To: <llvm.org/llvm/llvm-project/pull/147766 at github.com>


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@@ -519,14 +519,53 @@ void reopen_std_stream(void) {
   if (!fp) return;
 
   stdout = fp; // Let's make them alias.
-  clang_analyzer_eval(fp == oldStdout);     // expected-warning {{UNKNOWN}}
-  clang_analyzer_eval(fp == stdout);        // expected-warning {{TRUE}} no-FALSE
-  clang_analyzer_eval(oldStdout == stdout); // expected-warning {{UNKNOWN}}
+  clang_analyzer_eval(fp == oldStdout);     // expected-warning {{FALSE}}
+  clang_analyzer_eval(fp == stdout);        // expected-warning {{TRUE}}
+  clang_analyzer_eval(oldStdout == stdout); // expected-warning {{FALSE}}
 }
 
 void only_success_path_does_not_alias_with_stdout(void) {
   if (stdout) return;
   FILE *f = fopen("/tmp/foof", "r"); // no-crash
+  clang_analyzer_eval(f == 0);// expected-warning {{TRUE}} expected-warning {{FALSE}}
   if (!f) return;
   fclose(f);
 }
+
+extern void do_something();
+
+void test_no_invalidate_at_system_call(int use_std) {
+  FILE *fd;
+  char *buf;
+
+  if (use_std) {
+    fd = stdin;
+  } else {
+    if ((fd = fopen("x/y/z", "r")) == NULL)
+      return;
+
+    clang_analyzer_eval(fd == stdin); // expected-warning{{FALSE}}
+    buf = (char *)malloc(100);
+    clang_analyzer_eval(fd == stdin); // expected-warning{{FALSE}}
+  }
+
+  if (fd != stdin)
+    fclose(fd);
+}
----------------
steakhal wrote:

If I read this correctly, the test intends to check if the `stdin` system global would not get invalidated after calling `malloc()` (or for that matter any other opaque system header fn), right?

Could we simplify this into:
```c++
auto orig_stdin = stdin;
free(malloc(10)); // calling some opaque system fns
clang_analyzer_eval(stdin == orig_stdin); // TRUE
```

Same suggestion goes to the next example too.

https://github.com/llvm/llvm-project/pull/147766