[lldb] Add test for running static initializers in expressions.

[teemperor]

Summary

While reading ClangExpressionParser source code I saw a bunch of code that
specifically handles running all the static initializers in expressions. The coverage
bot tells me that we never actually test this code anywhere, so let's add some
testing to that feature.

[teemperor]

Just dumping this here because I don't want to anger the build bots before going into the weekend.

[teemperor]

Landed in r375422

lldb/packages/Python/lldbsuite/test/commands/expression/static-initializers/Makefile

+CXX_SOURCES := main.cpp
+
+include Makefile.rules

lldb/packages/Python/lldbsuite/test/commands/expression/static-initializers/TestStaticInitializers.py

+import lldb
+from lldbsuite.test.decorators import *
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test import lldbutil
+
+class StaticInitializers(TestBase):
+
+    mydir = TestBase.compute_mydir(__file__)
+
+    def test(self):
+        """ Test a static initializer. """
+        self.build()
+
+        lldbutil.run_to_source_breakpoint(self, '// break here',
+                lldb.SBFileSpec("main.cpp", False))
+
+        # We use counter to observe if the initializer was called.
+        self.expect("expr counter", substrs=["(int) $", " = 0"])
+        self.expect("expr -p -- struct Foo { Foo() { inc_counter(); } }; Foo f;")
+        self.expect("expr counter", substrs=["(int) $", " = 1"])
+
+    def test_failing_init(self):
+        """ Test a static initializer that fails to execute. """
+        self.build()
+
+        lldbutil.run_to_source_breakpoint(self, '// break here',
+                lldb.SBFileSpec("main.cpp", False))
+
+        # FIXME: This error message is not even remotely helpful.
+        self.expect("expr -p -- struct Foo2 { Foo2() { do_abort(); } }; Foo2 f;", error=True,
+                    substrs=["error: couldn't run static initializers: couldn't run static initializer:"])

lldb/packages/Python/lldbsuite/test/commands/expression/static-initializers/main.cpp

+#include <cstdlib>
+
+int counter = 0;
+
+void inc_counter() { ++counter; }
+
+void do_abort() { abort(); }
+
+int main() {
+  return 0; // break here
+}