Bug 213667

I recently changed the build system so that all files are included in the build, specifically because it simplifies the build system greatly.  I'd rather not re-introduce conditional compilation stuff.

What would the section notes to the linker look like?

They are just missing in those empty object files.

For ppc64-aix5 for instance the section notes are not in the source file (I assume because it is not normally assembled with gnu as) and for x86-linux it is excluded by the #ifdef when building on amd64.

> scanelf -qeR .
!WX --- ---  ./libcoregrind_amd64_linux_a-syscall-ppc64-aix5.o
!WX --- ---  ./libcoregrind_amd64_linux_a-syscall-amd64-darwin.o
!WX --- ---  ./libcoregrind_amd64_linux_a-m_start-amd64-darwin.o
!WX --- ---  ./libcoregrind_amd64_linux_a-dispatch-ppc64-aix5.o
!WX --- ---  ./libcoregrind_x86_linux_a-syscall-x86-darwin.o
!WX --- ---  ./libcoregrind_amd64_linux_a-mach_traps-amd64-darwin.o
!WX --- ---  ./libcoregrind_x86_linux_a-dispatch-amd64-darwin.o
!WX --- ---  ./libcoregrind_x86_linux_a-syscall-amd64-darwin.o
!WX --- ---  ./libcoregrind_x86_linux_a-syscall-amd64-linux.o
!WX --- ---  ./libcoregrind_x86_linux_a-dispatch-x86-darwin.o
!WX --- ---  ./libcoregrind_x86_linux_a-dispatch-ppc64-aix5.o
!WX --- ---  ./libcoregrind_amd64_linux_a-syscall-x86-darwin.o
!WX --- ---  ./libcoregrind_amd64_linux_a-dispatch-ppc32-aix5.o
!WX --- ---  ./libcoregrind_x86_linux_a-m_start-amd64-darwin.o
!WX --- ---  ./libcoregrind_x86_linux_a-mach_traps-x86-darwin.o
!WX --- ---  ./libcoregrind_amd64_linux_a-syscall-ppc32-linux.o
!WX --- ---  ./libcoregrind_x86_linux_a-m_start-x86-darwin.o
!WX --- ---  ./libcoregrind_x86_linux_a-mach_traps-amd64-darwin.o
!WX --- ---  ./libcoregrind_amd64_linux_a-syscall-x86-linux.o
!WX --- ---  ./libcoregrind_amd64_linux_a-syscall-ppc32-aix5.o
!WX --- ---  ./libcoregrind_x86_linux_a-syscall-ppc64-aix5.o
!WX --- ---  ./libcoregrind_amd64_linux_a-m_start-x86-darwin.o
!WX --- ---  ./libcoregrind_amd64_linux_a-dispatch-x86-darwin.o
!WX --- ---  ./libcoregrind_x86_linux_a-dispatch-ppc32-aix5.o
!WX --- ---  ./libcoregrind_amd64_linux_a-dispatch-x86-linux.o
!WX --- ---  ./libcoregrind_x86_linux_a-dispatch-ppc64-linux.o
!WX --- ---  ./libcoregrind_x86_linux_a-syscall-ppc32-aix5.o
!WX --- ---  ./libcoregrind_x86_linux_a-dispatch-amd64-linux.o
!WX --- ---  ./libcoregrind_amd64_linux_a-mach_traps-x86-darwin.o
!WX --- ---  ./libcoregrind_amd64_linux_a-dispatch-ppc32-linux.o
!WX --- ---  ./libcoregrind_amd64_linux_a-dispatch-amd64-darwin.o
!WX --- ---  ./libcoregrind_amd64_linux_a-dispatch-ppc64-linux.o
!WX --- ---  ./libcoregrind_x86_linux_a-syscall-ppc32-linux.o
!WX --- ---  ./libcoregrind_amd64_linux_a-syscall-ppc64-linux.o
!WX --- ---  ./libcoregrind_x86_linux_a-dispatch-ppc32-linux.o
!WX --- ---  ./libcoregrind_x86_linux_a-syscall-ppc64-linux.o


> readelf -S ./libcoregrind_amd64_linux_a-syscall-ppc64-aix5.o
There are 7 section headers, starting at offset 0x70:

Section Headers:
  [Nr] Name              Type             Address           Offset
       Size              EntSize          Flags  Link  Info  Align
  [ 0]                   NULL             0000000000000000  00000000
       0000000000000000  0000000000000000           0     0     0
  [ 1] .text             PROGBITS         0000000000000000  00000040
       0000000000000000  0000000000000000  AX       0     0     4
  [ 2] .data             PROGBITS         0000000000000000  00000040
       0000000000000000  0000000000000000  WA       0     0     4
  [ 3] .bss              NOBITS           0000000000000000  00000040
       0000000000000000  0000000000000000  WA       0     0     4
  [ 4] .shstrtab         STRTAB           0000000000000000  00000040
       000000000000002c  0000000000000000           0     0     1
  [ 5] .symtab           SYMTAB           0000000000000000  00000230
       0000000000000060  0000000000000018           6     4     8
  [ 6] .strtab           STRTAB           0000000000000000  00000290
       0000000000000001  0000000000000000           0     0     1
Key to Flags:
  W (write), A (alloc), X (execute), M (merge), S (strings)
  I (info), L (link order), G (group), x (unknown)
  O (extra OS processing required) o (OS specific), p (processor specific)
>

I don't think that we are going to change this. It may be a bit inefficient and require some conditional compilation but it seems to work reasonably well for all our dev, nightly and buildbot machines.