Object: Align resource sections correctly.

[pcc]

Summary

Previously we were using the default alignment, i.e. an alignment
of 16. This was more aligned than we needed to be and didn't match
cvtres's behaviour. This change sets the alignment to 1, as cvtres
does.

[hans]

I tried to verify this, but it seems cvtres.exe does not set alignment for the .rsrc sections:

rc /fo test_resource.res /nologo test_resource.rc && cvtres /machine:X86 /readonly /nologo /out:test_resource.obj.coff test_resource.res && dumpbin /headers test_resource.obj.coff
test_resource.rc(8) : warning RC4204 : ASCII character not equivalent to virtual key code
Microsoft (R) COFF/PE Dumper Version 14.12.25834.0
Copyright (C) Microsoft Corporation.  All rights reserved.


Dump of file test_resource.obj.coff

File Type: COFF OBJECT

FILE HEADER VALUES
             14C machine (x86)
               3 number of sections
        5AEC2266 time date stamp Fri May  4 11:05:42 2018
             C38 file pointer to symbol table
              10 number of symbols
               0 size of optional header
             100 characteristics
                   32 bit word machine

SECTION HEADER #1
.debug$S name
       0 physical address
       0 virtual address
     13C size of raw data
      8C file pointer to raw data (0000008C to 000001C7)
       0 file pointer to relocation table
       0 file pointer to line numbers
       0 number of relocations
       0 number of line numbers
42100040 flags
         Initialized Data
         Discardable
         1 byte align
         Read Only

SECTION HEADER #2
.rsrc$01 name
       0 physical address
       0 virtual address
     290 size of raw data
     1C8 file pointer to raw data (000001C8 to 00000457)
     458 file pointer to relocation table
       0 file pointer to line numbers
       8 number of relocations
       0 number of line numbers
40000040 flags
         Initialized Data
         (no align specified)
         Read Only

SECTION HEADER #3
.rsrc$02 name
       0 physical address
       0 virtual address
     790 size of raw data
     4A8 file pointer to raw data (000004A8 to 00000C37)
       0 file pointer to relocation table
       0 file pointer to line numbers
       0 number of relocations
       0 number of line numbers
40000040 flags
         Initialized Data
         (no align specified)
         Read Only

  Summary

         13C .debug$S
         290 .rsrc$01
         790 .rsrc$02

[hans]

cvtres.exe also doesn't seem to set the IMAGE_SCN_TYPE_NO_PAD flag:

obj2yaml.exe test_resource.obj.coff | grep -B1 Characteristics
  Machine:         IMAGE_FILE_MACHINE_I386
  Characteristics: [ IMAGE_FILE_32BIT_MACHINE ]
--
  - Name:            '.debug$S'
    Characteristics: [ IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_MEM_DISCARDABLE, IMAGE_SCN_MEM_READ ]
--
  - Name:            '.rsrc$01'
    Characteristics: [ IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_MEM_READ ]
--
  - Name:            '.rsrc$02'
    Characteristics: [ IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_MEM_READ ]

[pcc]

You're right, I was using the wrong obj2yaml binary to look at the object file :-/

llvm/lib/Object/WindowsResource.cpp

void WindowsResourceCOFFWriter::writeFirstSectionHeader() {
   SectionOneHeader->VirtualSize = 0;
   SectionOneHeader->VirtualAddress = 0;
   SectionOneHeader->SizeOfRawData = SectionOneSize;
   SectionOneHeader->PointerToRawData = SectionOneOffset;
   SectionOneHeader->PointerToRelocations = SectionOneRelocations;
   SectionOneHeader->PointerToLinenumbers = 0;
   SectionOneHeader->NumberOfRelocations = Data.size();
   SectionOneHeader->NumberOfLinenumbers = 0;
-  SectionOneHeader->Characteristics += COFF::IMAGE_SCN_CNT_INITIALIZED_DATA;
-  SectionOneHeader->Characteristics += COFF::IMAGE_SCN_MEM_READ;
+  SectionOneHeader->Characteristics = COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
+                                      COFF::IMAGE_SCN_MEM_READ |
+                                      COFF::IMAGE_SCN_ALIGN_1BYTES;
 }
 
 void WindowsResourceCOFFWriter::writeSecondSectionHeader() {
   // Write the second section header.
   CurrentOffset += sizeof(coff_section);
   auto *SectionTwoHeader =
       reinterpret_cast<coff_section *>(BufferStart + CurrentOffset);
   strncpy(SectionTwoHeader->Name, ".rsrc$02", (size_t)COFF::NameSize);
   SectionTwoHeader->VirtualSize = 0;
   SectionTwoHeader->VirtualAddress = 0;
   SectionTwoHeader->SizeOfRawData = SectionTwoSize;
   SectionTwoHeader->PointerToRawData = SectionTwoOffset;
   SectionTwoHeader->PointerToRelocations = 0;
   SectionTwoHeader->PointerToLinenumbers = 0;
   SectionTwoHeader->NumberOfRelocations = 0;
   SectionTwoHeader->NumberOfLinenumbers = 0;
-  SectionTwoHeader->Characteristics = COFF::IMAGE_SCN_CNT_INITIALIZED_DATA;
-  SectionTwoHeader->Characteristics += COFF::IMAGE_SCN_MEM_READ;
+  SectionTwoHeader->Characteristics = COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
+                                      COFF::IMAGE_SCN_MEM_READ |
+                                      COFF::IMAGE_SCN_ALIGN_1BYTES;
 }
 
 void WindowsResourceCOFFWriter::writeFirstSection() {
   // Write section one.
   CurrentOffset += sizeof(coff_section);
 
   writeDirectoryTree();
   writeDirectoryStringTable();

llvm/test/tools/llvm-cvtres/object.test

 // Check COFF emission of cvtres
 // The input was generated with the following command, using the original Windows
 // rc.exe:
 // > rc /fo test_resource.res /nologo test_resource.rc
 // The object file we are comparing against was generated with this command using
 // the original Windows cvtres.exe.
 // > cvtres /machine:X86 /readonly /nologo /out:test_resource.obj.coff \
 //   test_resource.res
 
 RUN: llvm-cvtres /verbose /out:%t %p/Inputs/test_resource.res
 RUN: llvm-readobj -coff-resources -section-data %t | FileCheck %s
+RUN: obj2yaml %t | FileCheck --check-prefix=SECTIONS %s
 
 CHECK:     Resources [
 CHECK-NEXT:  Total Number of Resources: 8
 CHECK-DAG:   Number of String Entries: 1
 CHECK-NEXT:  Number of ID Entries: 4
 CHECK-NEXT:  Type: STRINGARRAY [
 CHECK-NEXT:    Table Offset: 0x38
 CHECK-NEXT:    Number of String Entries: 1

 CHECK-NEXT:    0720: 00000000 00006400 66006900 73006800  |......d.f.i.s.h.|
 CHECK-NEXT:    0730: 00000000 65007300 61006C00 61006400  |....e.s.a.l.a.d.|
 CHECK-NEXT:    0740: 00008000 66006400 75006300 6B000000  |....f.d.u.c.k...|
 CHECK-NEXT:    0750: 74686973 20697320 61207573 65722064  |this is a user d|
 CHECK-NEXT:    0760: 6566696E 65642072 65736F75 72636500  |efined resource.|
 CHECK-NEXT:    0770: 69742063 6F6E7461 696E7320 6D616E79  |it contains many|
 CHECK-NEXT:    0780: 20737472 696E6773 00000000 00000000  | strings........|
 CHECK-NEXT:  )
+
+SECTIONS:      - Name:            '.rsrc$01'
+SECTIONS-NEXT:   Characteristics: [ IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_MEM_READ ]
+SECTIONS-NEXT:   Alignment:       1
+
+SECTIONS:      - Name:            '.rsrc$02'
+SECTIONS-NEXT:   Characteristics: [ IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_MEM_READ ]
+SECTIONS-NEXT:   Alignment:       1