Add pretty printing of Clang "bitfield" enums

Summary:
Using enumerators as flags is standard practice. This patch adds
support to LLDB to display such enum values symbolically, eg:

(E) e1 = A | B

If enumerators don't cover the whole value, the remaining bits are
displayed as hexadecimal:

(E) e4 = A | 0x10

Detecting whether an enum is used as a bitfield or not is
complicated. This patch implements a heuristic that assumes that such
enumerators will either have only 1 bit set or will be a combination
of previous values.

This patch doesn't change the way we currently display enums which the
above heuristic would not consider as bitfields.

Reviewers: jingham, labath

Subscribers: lldb-commits

Differential Revision: https://reviews.llvm.org/D67520

llvm-svn: 374067

2 files changed, 46 insertions, 3 deletions

diff --git a/lldb/packages/Python/lldbsuite/test/lang/c/enum_types/TestEnumTypes.py b/lldb/packages/Python/lldbsuite/test/lang/c/enum_types/TestEnumTypes.py
index f6cf3c7f67c..7ab1199fa95 100644
--- a/lldb/packages/Python/lldbsuite/test/lang/c/enum_types/TestEnumTypes.py
+++ b/lldb/packages/Python/lldbsuite/test/lang/c/enum_types/TestEnumTypes.py
@@ -25,11 +25,35 @@ class EnumTypesTestCase(TestBase):
         exe = self.getBuildArtifact("a.out")
         self.runCmd("file " + exe, CURRENT_EXECUTABLE_SET)
 
+        lldbutil.run_to_source_breakpoint(
+            self, '// Breakpoint for bitfield', lldb.SBFileSpec("main.c"))
+
+        self.expect("fr var a", DATA_TYPES_DISPLAYED_CORRECTLY,
+                    patterns=[' = A$'])
+        self.expect("fr var b", DATA_TYPES_DISPLAYED_CORRECTLY,
+                    patterns=[' = B$'])
+        self.expect("fr var c", DATA_TYPES_DISPLAYED_CORRECTLY,
+                    patterns=[' = C$'])
+        self.expect("fr var ab", DATA_TYPES_DISPLAYED_CORRECTLY,
+                    patterns=[' = AB$'])
+        self.expect("fr var ac", DATA_TYPES_DISPLAYED_CORRECTLY,
+                    patterns=[' = A | C$'])
+        self.expect("fr var all", DATA_TYPES_DISPLAYED_CORRECTLY,
+                    patterns=[' = ALL$'])
+        # Test that an enum that doesn't match the heuristic we use in
+        # ClangASTContext::DumpEnumValue, gets printed as a raw integer.
+        self.expect("fr var omega", DATA_TYPES_DISPLAYED_CORRECTLY,
+                    patterns=[' = 7$'])
+        # Test the behavior in case have a variable of a type considered
+        # 'bitfield' by the heuristic, but the value isn't actually fully
+        # covered by the enumerators.
+        self.expect("p (enum bitfield)nonsense", DATA_TYPES_DISPLAYED_CORRECTLY,
+                    patterns=[' = B | C | 0x10$'])
+
         # Break inside the main.
         bkpt_id = lldbutil.run_break_set_by_file_and_line(
             self, "main.c", self.line, num_expected_locations=1, loc_exact=True)
-
-        self.runCmd("run", RUN_SUCCEEDED)
+        self.runCmd("c", RUN_SUCCEEDED)
 
         # The stop reason of the thread should be breakpoint.
         self.expect("thread list", STOPPED_DUE_TO_BREAKPOINT,
diff --git a/lldb/packages/Python/lldbsuite/test/lang/c/enum_types/main.c b/lldb/packages/Python/lldbsuite/test/lang/c/enum_types/main.c
index 924336e97e0..675af5ecec5 100644
--- a/lldb/packages/Python/lldbsuite/test/lang/c/enum_types/main.c
+++ b/lldb/packages/Python/lldbsuite/test/lang/c/enum_types/main.c
@@ -18,6 +18,20 @@ struct foo {
 
 int main (int argc, char const *argv[])
 {
+    enum bitfield {
+        None = 0,
+        A = 1 << 0,
+        B = 1 << 1,
+        C = 1 << 2,
+        AB = A | B,
+        ALL = A | B | C,
+    };
+
+    enum non_bitfield {
+        Alpha = 3,
+        Beta = 4
+    };
+
     enum days {
         Monday = -3,
         Tuesday,
@@ -28,9 +42,14 @@ int main (int argc, char const *argv[])
         Sunday,
         kNumDays
     };
+
+    enum bitfield a = A, b = B, c = C, ab = AB, ac = A | C, all = ALL;
+    int nonsense = a + b + c + ab + ac + all;
+    enum non_bitfield omega = Alpha | Beta;
+
     enum days day;
     struct foo f;
-    f.op = NULL;
+    f.op = NULL; // Breakpoint for bitfield
     for (day = Monday - 1; day <= kNumDays + 1; day++)
     {
         printf("day as int is %i\n", (int)day); // Set break point at this line.