[LLDB] Fix the handling of unnamed bit-fields when parsing DWARF

We ran into an assert when debugging clang and performing an expression on a class derived from DeclContext. The assert was indicating we were getting the offsets wrong for RecordDeclBitfields. We were getting both the size and offset of unnamed bit-field members wrong. We could fix this case with a quick change but as I extended the test suite to include more combinations we kept finding more cases that were being handled incorrectly. A fix that handled all the new cases as well as the cases already covered required a refactor of the existing technique.

Differential Revision: https://reviews.llvm.org/D72953

(cherry picked from commit fcaf5f6)

Author: shafik

lldb/packages/Python/lldbsuite/test/lang/cpp/bitfields/Makefile

@@ -0,0 +1,3 @@
+CXX_SOURCES := main.cpp
+
+include Makefile.rules

lldb/packages/Python/lldbsuite/test/lang/cpp/bitfields/TestCppBitfields.py

@@ -0,0 +1,105 @@
+"""Show bitfields and check that they display correctly."""
+
+import lldb
+from lldbsuite.test.decorators import *
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test import lldbutil
+
+
+class CppBitfieldsTestCase(TestBase):
+
+    mydir = TestBase.compute_mydir(__file__)
+
+    def setUp(self):
+        # Call super's setUp().
+        TestBase.setUp(self)
+        # Find the line number to break inside main().
+        self.line = line_number('main.cpp', '// Set break point at this line.')
+
+    # BitFields exhibit crashes in record layout on Windows
+    # (http://llvm.org/pr21800)
+    @skipIfWindows
+    def test_and_run_command(self):
+        """Test 'frame variable ...' on a variable with bitfields."""
+        self.build()
+
+        lldbutil.run_to_source_breakpoint(self, '// Set break point at this line.',
+          lldb.SBFileSpec("main.cpp", False))
+
+        # The stop reason of the thread should be breakpoint.
+        self.expect("thread list", STOPPED_DUE_TO_BREAKPOINT,
+                    substrs=['stopped',
+                             'stop reason = breakpoint'])
+
+        # The breakpoint should have a hit count of 1.
+        self.expect("breakpoint list -f", BREAKPOINT_HIT_ONCE,
+                    substrs=[' resolved, hit count = 1'])
+
+        self.expect("expr (lba.a)", VARIABLES_DISPLAYED_CORRECTLY,
+                    substrs=['unsigned int', '2'])
+        self.expect("expr (lbb.b)", VARIABLES_DISPLAYED_CORRECTLY,
+                    substrs=['unsigned int', '3'])
+        self.expect("expr (lbc.c)", VARIABLES_DISPLAYED_CORRECTLY,
+                    substrs=['unsigned int', '4'])
+        self.expect("expr (lbd.a)", VARIABLES_DISPLAYED_CORRECTLY,
+                    substrs=['unsigned int', '5'])
+        self.expect("expr (clang_example.f.a)", VARIABLES_DISPLAYED_CORRECTLY,
+                    substrs=['uint64_t', '1'])
+
+        self.expect(
+            "frame variable --show-types lba",
+            VARIABLES_DISPLAYED_CORRECTLY,
+            substrs=[
+                '(int:32)  = ',
+                '(unsigned int:20) a = 2',
+                ])
+
+        self.expect(
+            "frame variable --show-types lbb",
+            VARIABLES_DISPLAYED_CORRECTLY,
+            substrs=[
+                '(unsigned int:1) a = 1',
+                '(int:31)  =',
+                '(unsigned int:20) b = 3',
+                ])
+
+        self.expect(
+            "frame variable --show-types lbc",
+            VARIABLES_DISPLAYED_CORRECTLY,
+            substrs=[
+                '(int:22)  =',
+                '(unsigned int:1) a = 1',
+                '(unsigned int:1) b = 0',
+                '(unsigned int:5) c = 4',
+                '(unsigned int:1) d = 1',
+                '(int:2)  =',
+                '(unsigned int:20) e = 20',
+                ])
+
+        self.expect(
+            "frame variable --show-types lbd",
+            VARIABLES_DISPLAYED_CORRECTLY,
+            substrs=[
+                '(char [3]) arr = "abc"',
+                '(int:32)  =',
+                '(unsigned int:20) a = 5',
+                ])
+
+        self.expect(
+            "frame variable --show-types clang_example",
+            VARIABLES_DISPLAYED_CORRECTLY,
+            substrs=[
+                   '(int:22)  =',
+                   '(uint64_t:1) a = 1',
+                   '(uint64_t:1) b = 0',
+                   '(uint64_t:1) c = 1',
+                   '(uint64_t:1) d = 0',
+                   '(uint64_t:1) e = 1',
+                   '(uint64_t:1) f = 0',
+                   '(uint64_t:1) g = 1',
+                   '(uint64_t:1) h = 0',
+                   '(uint64_t:1) i = 1',
+                   '(uint64_t:1) j = 0',
+                   '(uint64_t:1) k = 1',
+                ])
+

lldb/packages/Python/lldbsuite/test/lang/cpp/bitfields/main.cpp

@@ -0,0 +1,81 @@
+#include <stdint.h>
+
+int main(int argc, char const *argv[]) {
+  struct LargeBitsA {
+    unsigned int : 30, a : 20;
+  } lba;
+
+  struct LargeBitsB {
+    unsigned int a : 1, : 11, : 12, b : 20;
+  } lbb;
+
+  struct LargeBitsC {
+    unsigned int : 13, : 9, a : 1, b : 1, c : 5, d : 1, e : 20;
+  } lbc;
+
+  struct LargeBitsD {
+    char arr[3];
+    unsigned int : 30, a : 20;
+  } lbd;
+
+  // This case came up when debugging clang and models RecordDeclBits
+  struct BitExampleFromClangDeclContext {
+    class fields {
+      uint64_t : 13;
+      uint64_t : 9;
+
+      uint64_t a: 1;
+      uint64_t b: 1;
+      uint64_t c: 1;
+      uint64_t d: 1;
+      uint64_t e: 1;
+      uint64_t f: 1;
+      uint64_t g: 1;
+      uint64_t h: 1;
+      uint64_t i: 1;
+      uint64_t j: 1;
+      uint64_t k: 1;
+
+      // In order to reproduce the crash for this case we need the
+      // members of fields to stay private :-(
+      friend struct BitExampleFromClangDeclContext;
+    };
+
+    union {
+      struct fields f;
+    };
+
+    BitExampleFromClangDeclContext() {
+  f.a = 1;
+  f.b = 0;
+  f.c = 1;
+  f.d = 0;
+  f.e = 1;
+  f.f = 0;
+  f.g = 1;
+  f.h = 0;
+  f.i = 1;
+  f.j = 0;
+  f.k = 1;
+    } 
+  } clang_example;
+
+  lba.a = 2;
+
+  lbb.a = 1;
+  lbb.b = 3;
+
+  lbc.a = 1;
+  lbc.b = 0;
+  lbc.c = 4;
+  lbc.d = 1;
+  lbc.e = 20;
+
+  lbd.arr[0] = 'a';
+  lbd.arr[1] = 'b';
+  lbd.arr[2] = 'c';
+  lbd.a = 5;
+
+
+  return 0; // Set break point at this line.
+}