[Lldb-commits] [lldb] r267248 - DWARF layout for bitfields is wrong when the bit offset is negative.

[Greg Clayton via lldb-commits]

Author: gclayton
Date: Fri Apr 22 18:14:35 2016
New Revision: 267248

URL: http://llvm.org/viewvc/llvm-project?rev=267248&view=rev
Log:
DWARF layout for bitfields is wrong when the bit offset is negative. 

Some older versions of clang emitted bit offsets that were negative and these bitfields would have their bitfield-ness stripped off and it would cause a clang assertion in clang assertions were enabled. I updated the bitfield C test to make sure we don't regress.

<rdar://problem/21082998> 


Modified:
    lldb/trunk/packages/Python/lldbsuite/test/lang/c/bitfields/TestBitfields.py
    lldb/trunk/packages/Python/lldbsuite/test/lang/c/bitfields/main.c
    lldb/trunk/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp

Modified: lldb/trunk/packages/Python/lldbsuite/test/lang/c/bitfields/TestBitfields.py
URL: http://llvm.org/viewvc/llvm-project/lldb/trunk/packages/Python/lldbsuite/test/lang/c/bitfields/TestBitfields.py?rev=267248&r1=267247&r2=267248&view=diff
==============================================================================
--- lldb/trunk/packages/Python/lldbsuite/test/lang/c/bitfields/TestBitfields.py (original)
+++ lldb/trunk/packages/Python/lldbsuite/test/lang/c/bitfields/TestBitfields.py Fri Apr 22 18:14:35 2016
@@ -96,6 +96,14 @@ class BitfieldsTestCase(TestBase):
         self.expect("expr (more_bits.d)", VARIABLES_DISPLAYED_CORRECTLY,
             substrs = ['uint8_t', '\\0'])
 
+        self.expect("expr (packed.a)", VARIABLES_DISPLAYED_CORRECTLY, 
+            substrs = ['char', "'a'"])
+        self.expect("expr (packed.b)", VARIABLES_DISPLAYED_CORRECTLY, 
+            substrs = ['uint32_t', "10"])
+        self.expect("expr/x (packed.c)", VARIABLES_DISPLAYED_CORRECTLY, 
+            substrs = ['uint32_t', "7112233"])
+
+
     @add_test_categories(['pyapi'])
     @skipIfWindows # BitFields exhibit crashes in record layout on Windows (http://llvm.org/pr21800)
     def test_and_python_api(self):

Modified: lldb/trunk/packages/Python/lldbsuite/test/lang/c/bitfields/main.c
URL: http://llvm.org/viewvc/llvm-project/lldb/trunk/packages/Python/lldbsuite/test/lang/c/bitfields/main.c?rev=267248&r1=267247&r2=267248&view=diff
==============================================================================
--- lldb/trunk/packages/Python/lldbsuite/test/lang/c/bitfields/main.c (original)
+++ lldb/trunk/packages/Python/lldbsuite/test/lang/c/bitfields/main.c Fri Apr 22 18:14:35 2016
@@ -8,6 +8,7 @@
 //===----------------------------------------------------------------------===//
 #include <stdint.h>
 #include <stdio.h>
+
 int main (int argc, char const *argv[])
 {
     struct Bits
@@ -62,6 +63,19 @@ int main (int argc, char const *argv[])
     more_bits.c = 1;
     more_bits.d = 0;
 
+#pragma pack(1)
+    struct PackedBits
+    {
+        char a;
+    	uint32_t b : 5,
+                 c : 27;
+    };
+#pragma pack()  
+    struct PackedBits packed;
+    packed.a = 'a';
+    packed.b = 10;
+    packed.c = 0x7112233;
+
     return 0;               //// Set break point at this line.
 
 }

Modified: lldb/trunk/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp
URL: http://llvm.org/viewvc/llvm-project/lldb/trunk/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp?rev=267248&r1=267247&r2=267248&view=diff
==============================================================================
--- lldb/trunk/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp (original)
+++ lldb/trunk/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp Fri Apr 22 18:14:35 2016
@@ -2671,7 +2671,7 @@ DWARFASTParserClang::ParseChildMembers(c
                     AccessType accessibility = eAccessNone;
                     uint32_t member_byte_offset = (parent_die.Tag() == DW_TAG_union_type) ? 0 : UINT32_MAX;
                     size_t byte_size = 0;
-                    size_t bit_offset = 0;
+                    int64_t bit_offset = 0;
                     size_t bit_size = 0;
                     bool is_external = false; // On DW_TAG_members, this means the member is static
                     uint32_t i;
@@ -2688,7 +2688,7 @@ DWARFASTParserClang::ParseChildMembers(c
                                 case DW_AT_decl_column: decl.SetColumn(form_value.Unsigned()); break;
                                 case DW_AT_name:        name = form_value.AsCString(); break;
                                 case DW_AT_type:        encoding_form = form_value; break;
-                                case DW_AT_bit_offset:  bit_offset = form_value.Unsigned(); break;
+                                case DW_AT_bit_offset:  bit_offset = form_value.Signed(); break;
                                 case DW_AT_bit_size:    bit_size = form_value.Unsigned(); break;
                                 case DW_AT_byte_size:   byte_size = form_value.Unsigned(); break;
                                 case DW_AT_data_member_location:
@@ -2802,7 +2802,7 @@ DWARFASTParserClang::ParseChildMembers(c
                     // type in an expression when clang becomes unhappy with its
                     // recycled debug info.
 
-                    if (bit_offset > 128)
+                    if (byte_size == 0 && bit_offset < 0)
                     {
                         bit_size = 0;
                         bit_offset = 0;