[PATCH] D30291: Handle section header flags redefinitions similar to GAS

[Rafael Avila de Espindola via llvm-commits]

Christof Douma via Phabricator <reviews at reviews.llvm.org> writes:
> -  MCSection *ELFSection = getContext().getELFSection(
> +  MCSectionELF *ELFSection = getContext().getELFSection(
>        SectionName, Type, Flags, Size, GroupName, UniqueID, Associated);
> +  // Sections are not identified by flags. Check if there is a mismatch in the
> +  // flags requested and the flags in the section returned. If the mismatch is
> +  // in OS or CPU specific flags, just add them. For any other mismatch warn
> +  // the user that we are ignoring the new flags.
> +  const unsigned overrideMask = (ELF::SHF_MASKOS | ELF::SHF_MASKPROC);
> +  unsigned curFlags = ELFSection->getFlags();
> +  curFlags |= Flags & overrideMask;
> +  Flags |= curFlags & overrideMask;
> +  ELFSection->setFlags(curFlags);
> +  if (curFlags != Flags)
> +    Warning(loc, "ignoring override of non-target sepecific section flags");
> +
>    getStreamer().SwitchSection(ELFSection, Subsection);

Are you should this is an intentional behaviour? It is hard to see why
it is a good thing for MASKPROC and MASKOS to be special.



>    if (getContext().getGenDwarfForAssembly()) {
>
>
> Index: test/MC/ELF/section-override-flags.s
> ===================================================================
> --- /dev/null
> +++ test/MC/ELF/section-override-flags.s
> @@ -0,0 +1,36 @@
> +// RUN: llvm-mc -filetype=obj -triple arm-pc-linux-gnu %s -o %t 2>&1 | FileCheck -check-prefix=DIAG %s
> +// RUN: llvm-readobj -s %t | FileCheck %s
> +
> +// REQUIRES: arm-registered-target

Just move the test to an ARM subdirectory.

> +// Test we handle overriding OS and PROC specific flags on the builtin .text section
> +.section .text,"0x200006",%progbits
> +.section .text,"0x40000006",%progbits


The distinction of builtin versus regular is also odd. The ELF spec has
no such terms.


> +// CHECK:      Section {
> +// CHECK:        Name: .text
> +// CHECK-NEXT:   Type: SHT_PROGBITS (0x1)
> +// CHECK-NEXT:   Flags [ (0x40200006)
> +// CHECK-NEXT:     SHF_ALLOC (0x2)
> +// CHECK-NEXT:     SHF_EXECINSTR (0x4)
> +// CHECK-NEXT:   ]
> +
> +//Attempt to override flags that are not target specific should be ignored
> +.section foo,"ax",%progbits
> +.section foo,"0x7",%progbits
> +.section foo,"0x10000007",%progbits
> +
> +// DIAG: warning: ignoring override of non-target sepecific section flags
> +// DIAG: warning: ignoring override of non-target sepecific section flags

Test the location.

Cheers,
Rafael