Add new elfmix.a ELF test file with a range of different file types.

Now that StaticLibFile is out of the way, show off ArFile's recursive
ability to:

- not care about the .a suffix and not behave differently depending on
  filenames;
- not crash and lose everything when some archive members are not ELF;
- gracefully fall back and run the next best tool for a cross-compiled
  ELF and a sample of non-ELF members - including the corresponding .c
  source.

Tests issue #64, see more details there.

In addition to the .c source file, the regen_elfmix.sh script that generated
the .a files is embedded in the .a files themselves if ever needed. For
size considerations no cross-compiler is provided.

Signed-off-by: Chris Lamb <lamby@debian.org>

Gbp-Dch: ignore

tests/comparators/test_elf.py

@@ -145,6 +145,49 @@ def test_lib_compare_non_existing(monkeypatch, lib1):
     assert len(difference.details) > 0
 
 
+TEST_LIBMIX1_PATH = data('elfmix1.not_a')
+TEST_LIBMIX2_PATH = data('elfmix2.a')
+
+
+@pytest.fixture
+def libmix1():
+    return specialize(FilesystemFile(TEST_LIBMIX1_PATH))
+
+
+@pytest.fixture
+def libmix2():
+    return specialize(FilesystemFile(TEST_LIBMIX2_PATH))
+
+
+@pytest.fixture
+def libmix_differences(libmix1, libmix2):
+    return libmix1.compare(libmix2).details
+
+
+@skip_unless_tools_exist('readelf', 'objdump')
+@skip_if_tool_version_is('readelf', readelf_version, '2.29')
+@skip_if_binutils_does_not_support_x86()
+def test_libmix_differences(libmix_differences):
+    assert len(libmix_differences) == 5
+    file_list, mach_o, x86_o, src_c, x_obj = libmix_differences
+
+    # Check order and basic identification
+    assert file_list.source1 == 'file list'
+    assert "Falling back to binary" in mach_o.comments[0]
+    x86_o = x86_o.details[0]
+    assert x86_o.source1.startswith('objdump ')
+    assert src_c.source1.endswith('.c')
+    x_obj = x_obj.details[0]
+    assert x_obj.source1.startswith('readelf ')
+
+    # Content
+    assert 'return42_or_3' in file_list.unified_diff
+    assert mach_o.unified_diff == get_data('elfmix_mach_o_expected_diff')
+    assert x86_o.unified_diff == get_data('elfmix_disassembly_expected_diff')
+    assert src_c.unified_diff == get_data('elfmix_src_c_expected_diff')
+    assert x_obj.unified_diff == get_data('elfmix_x_obj_expected_diff')
+
+
 TEST_DBGSYM_DEB1_PATH = data('dbgsym/add/test-dbgsym_1_amd64.deb')
 TEST_DBGSYM_DEB2_PATH = data('dbgsym/mult/test-dbgsym_1_amd64.deb')
 

tests/data/elfmix_disassembly_expected_diff

+@@ -3,10 +3,10 @@
+ 
+ Disassembly of section .text:
+ 
+ 0000000000000000 <return42_or_3>:
+ return42_or_3():
+    0:	55                   	push   %rbp
+    1:	48 89 e5             	mov    %rsp,%rbp
+-   4:	b8 2a 00 00 00       	mov    $0x2a,%eax
++   4:	b8 2b 00 00 00       	mov    $0x2b,%eax
+    9:	5d                   	pop    %rbp
+    a:	c3                   	retq   

tests/data/elfmix_mach_o_expected_diff

+@@ -23,15 +23,15 @@
+ 00000160: 0100 0000 000e 0a00 000e 0a00 0000 0000  ................
+ 00000170: 0200 0000 1800 0000 5002 0000 0100 0000  ........P.......
+ 00000180: 6002 0000 1000 0000 0b00 0000 5000 0000  `...........P...
+ 00000190: 0000 0000 0000 0000 0000 0000 0100 0000  ................
+ 000001a0: 0100 0000 0000 0000 0000 0000 0000 0000  ................
+ 000001b0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
+ 000001c0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
+-000001d0: 0000 0000 0000 0000 5548 89e5 b82a 0000  ........UH...*..
++000001d0: 0000 0000 0000 0000 5548 89e5 b82b 0000  ........UH...+..
+ 000001e0: 005d c300 0000 0000 0000 0000 0000 0000  .]..............
+ 000001f0: 0b00 0000 0000 0001 0000 0000 0000 0000  ................
+ 00000200: 0000 0000 0000 0000 1400 0000 0000 0000  ................
+ 00000210: 017a 5200 0178 1001 100c 0708 9001 0000  .zR..x..........
+ 00000220: 2400 0000 1c00 0000 b0ff ffff ffff ffff  $...............
+ 00000230: 0b00 0000 0000 0000 0041 0e10 8602 430d  .........A....C.
+ 00000240: 0600 0000 0000 0000 0000 0000 0100 0006  ................

tests/data/elfmix_src_c_expected_diff

+@@ -1,5 +1,5 @@
+ 
+ int return42_or_3()
+ {
+-  return 42; // for sed
++  return 43; // for sed
+ }

tests/data/elfmix_x_obj_expected_diff

+@@ -1,4 +1,4 @@
+ 
+ Hex dump of section '.text':
+-  0x00000000 3641007d 012ca21d f0                6A.}.,...
++  0x00000000 3641007d 012cb21d f0                6A.}.,...
+