[lld] r262650 - [ELF] - Do not allow .bss to occupy the file space when producing relocatable output

[George Rimar via llvm-commits]

Author: grimar
Date: Thu Mar  3 14:24:14 2016
New Revision: 262650

URL: http://llvm.org/viewvc/llvm-project?rev=262650&view=rev
Log:
[ELF] - Do not allow .bss to occupy the file space when producing relocatable output

When generating relocatable output SHT_NOBITS sections
were still occupy the file space.

Differential revision: http://reviews.llvm.org/D17857

Added:
    lld/trunk/test/ELF/relocatable-bss.s
Modified:
    lld/trunk/ELF/Writer.cpp
    lld/trunk/test/ELF/relocatable.s

Modified: lld/trunk/ELF/Writer.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Writer.cpp?rev=262650&r1=262649&r2=262650&view=diff
==============================================================================
--- lld/trunk/ELF/Writer.cpp (original)
+++ lld/trunk/ELF/Writer.cpp Thu Mar  3 14:24:14 2016
@@ -1327,9 +1327,11 @@ template <class ELFT> void Writer<ELFT>:
   Out<ELFT>::ElfHeader->setSize(sizeof(Elf_Ehdr));
   uintX_t FileOff = 0;
   for (OutputSectionBase<ELFT> *Sec : OutputSections) {
-    FileOff = alignTo(FileOff, Sec->getAlign());
+    if (Sec->getType() != SHT_NOBITS)
+      FileOff = alignTo(FileOff, Sec->getAlign());
     Sec->setFileOffset(FileOff);
-    FileOff += Sec->getSize();
+    if (Sec->getType() != SHT_NOBITS)
+      FileOff += Sec->getSize();
   }
   SectionHeaderOff = alignTo(FileOff, sizeof(uintX_t));
   FileSize = SectionHeaderOff + getNumSections() * sizeof(Elf_Shdr);

Added: lld/trunk/test/ELF/relocatable-bss.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/relocatable-bss.s?rev=262650&view=auto
==============================================================================
--- lld/trunk/test/ELF/relocatable-bss.s (added)
+++ lld/trunk/test/ELF/relocatable-bss.s Thu Mar  3 14:24:14 2016
@@ -0,0 +1,40 @@
+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t1.o
+# RUN: ld.lld -r %t1.o -o %t
+# RUN: llvm-readobj -file-headers -sections -program-headers -symbols -r %t | FileCheck %s
+
+## We check here that .bss does not occupy the space in file.
+## If it would, the SectionHeaderOffset would have offset about 5 megabytes.
+# CHECK:       ElfHeader {
+# CHECK-NEXT:  Ident {
+# CHECK-NEXT:    Magic: (7F 45 4C 46)
+# CHECK-NEXT:    Class: 64-bit
+# CHECK-NEXT:    DataEncoding: LittleEndian
+# CHECK-NEXT:    FileVersion: 1
+# CHECK-NEXT:    OS/ABI: SystemV
+# CHECK-NEXT:    ABIVersion: 0
+# CHECK-NEXT:    Unused: (00 00 00 00 00 00 00)
+# CHECK-NEXT:  }
+# CHECK-NEXT:  Type: Relocatable
+# CHECK-NEXT:  Machine: EM_X86_64
+# CHECK-NEXT:  Version:
+# CHECK-NEXT:  Entry:
+# CHECK-NEXT:   ProgramHeaderOffset:
+# CHECK-NEXT:   SectionHeaderOffset: 0xA8
+# CHECK-NEXT:  Flags [
+# CHECK-NEXT:  ]
+# CHECK-NEXT:  HeaderSize:
+# CHECK-NEXT:  ProgramHeaderEntrySize:
+# CHECK-NEXT:  ProgramHeaderCount:
+# CHECK-NEXT:  SectionHeaderEntrySize:
+# CHECK-NEXT:  SectionHeaderCount:
+# CHECK-NEXT:  StringTableSectionIndex:
+# CHECK-NEXT:  }
+
+.text
+.globl _start;
+_start:
+ nop
+
+.bss
+ .space 5242880

Modified: lld/trunk/test/ELF/relocatable.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/relocatable.s?rev=262650&r1=262649&r2=262650&view=diff
==============================================================================
--- lld/trunk/test/ELF/relocatable.s (original)
+++ lld/trunk/test/ELF/relocatable.s Thu Mar  3 14:24:14 2016
@@ -30,7 +30,7 @@
 # CHECK-NEXT:  Version: 1
 # CHECK-NEXT:  Entry: 0x0
 # CHECK-NEXT:  ProgramHeaderOffset: 0x0
-# CHECK-NEXT:  SectionHeaderOffset: 0x2D8
+# CHECK-NEXT:  SectionHeaderOffset: 0x2C0
 # CHECK-NEXT:  Flags [
 # CHECK-NEXT:  ]
 # CHECK-NEXT:  HeaderSize: 64