[libunwind] r297174 - Improve readability and correctness of the OS specific libunwind bits.

[Asiri Rathnayake via cfe-commits]

Hi Ed,

Could you please always include cfe-commits as a subscriber in you phab
reviews?

We would like to be aware of these changes in advance before they land.

Thanks.

/ Asiri


On 7 Mar 2017 6:27 p.m., "Ed Schouten via cfe-commits" <
cfe-commits at lists.llvm.org> wrote:

> Author: ed
> Date: Tue Mar  7 12:15:52 2017
> New Revision: 297174
>
> URL: http://llvm.org/viewvc/llvm-project?rev=297174&view=rev
> Log:
> Improve readability and correctness of the OS specific libunwind bits.
>
> All of the access to __exidx_*, dl_iterate_phdr(), etc. is specific to
> the findUnwindSections() function. Right now all of the includes and
> declarations related to them are scattered throughout the source file.
> For example, for <link.h>, we have a full list of operating systems
> guarding the #include, even though the code that uses dl_iterate_phdr()
> miraculously doesn't use the same list.
>
> Change the code so that findUnwindSections() is preceded by a block of
> #ifdefs that share the same structure as the function itself. First
> comes all of the macOS specific bits, followed by bare-metal ARM,
> followed by ELF EHABI + DWARF.
>
> This actually allows us to build a copy of libunwind without any
> specific ifdefs for NetBSD, CloudABI, etc. It likely also unbreaks the
> build of libunwind on FreeBSD/armv6, though I can't confirm.
>
> Reviewed by:    compnerd
> Differential Revision:  https://reviews.llvm.org/D30696
>
> Modified:
>     libunwind/trunk/src/AddressSpace.hpp
>
> Modified: libunwind/trunk/src/AddressSpace.hpp
> URL: http://llvm.org/viewvc/llvm-project/libunwind/trunk/src/
> AddressSpace.hpp?rev=297174&r1=297173&r2=297174&view=diff
> ============================================================
> ==================
> --- libunwind/trunk/src/AddressSpace.hpp (original)
> +++ libunwind/trunk/src/AddressSpace.hpp Tue Mar  7 12:15:52 2017
> @@ -34,32 +34,6 @@ namespace libunwind {
>  #include "dwarf2.h"
>  #include "Registers.hpp"
>
> -#if _LIBUNWIND_ARM_EHABI
> -#if defined(_LIBUNWIND_IS_BAREMETAL)
> -// When statically linked on bare-metal, the symbols for the EH table are
> looked
> -// up without going through the dynamic loader.
> -extern char __exidx_start;
> -extern char __exidx_end;
> -#else
> -#include <link.h>
> -#endif // !defined(_LIBUNWIND_IS_BAREMETAL)
> -#endif // _LIBUNWIND_ARM_EHABI
> -
> -#if defined(__CloudABI__) || defined(__FreeBSD__) || defined(__Fuchsia__)
> ||  \
> -    defined(__linux__) || defined(__NetBSD__)
> -#if _LIBUNWIND_SUPPORT_DWARF_UNWIND && _LIBUNWIND_SUPPORT_DWARF_INDEX
> -#include <link.h>
> -// Macro for machine-independent access to the ELF program headers. This
> -// macro is not available on some systems (e.g., FreeBSD). On these
> -// systems the data structures are just called Elf_XXX. Define ElfW()
> -// locally.
> -#if !defined(ElfW)
> -#define ElfW(type) Elf_##type
> -#endif
> -#include "EHHeaderParser.hpp"
> -#endif
> -#endif
> -
>  namespace libunwind {
>
>  /// Used by findUnwindSections() to return info about needed sections.
> @@ -291,6 +265,7 @@ LocalAddressSpace::getEncodedP(pint_t &a
>  }
>
>  #ifdef __APPLE__
> +
>    struct dyld_unwind_sections
>    {
>      const struct mach_header*   mh;
> @@ -336,6 +311,30 @@ LocalAddressSpace::getEncodedP(pint_t &a
>        return true;
>      }
>    #endif
> +
> +#elif _LIBUNWIND_ARM_EHABI && defined(_LIBUNWIND_IS_BAREMETAL)
> +
> +// When statically linked on bare-metal, the symbols for the EH table are
> looked
> +// up without going through the dynamic loader.
> +extern char __exidx_start;
> +extern char __exidx_end;
> +
> +#elif _LIBUNWIND_ARM_EHABI || _LIBUNWIND_SUPPORT_DWARF_UNWIND
> +
> +// ELF-based systems may use dl_iterate_phdr() to access sections
> +// containing unwinding information. The ElfW() macro for pointer-size
> +// independent ELF header traversal is not provided by <link.h> on some
> +// systems (e.g., FreeBSD). On these systems the data structures are
> +// just called Elf_XXX. Define ElfW() locally.
> +#include <link.h>
> +#if !defined(ElfW)
> +#define ElfW(type) Elf_##type
> +#endif
> +
> +#if _LIBUNWIND_SUPPORT_DWARF_UNWIND
> +#include "EHHeaderParser.hpp"
> +#endif
> +
>  #endif
>
>  inline bool LocalAddressSpace::findUnwindSections(pint_t targetAddr,
>
>
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