Re: Work around non-existence of ElfW(type) macro on FreeBSD

[gAlfonso-bit]

Summary

FreeBSD contributor here! Although this code works, this is not the first time this macro comes up, and the way it is defined is a little different. Because of this, the workaround that is used is

#if !defined(ElfW)
#define ElfW(type) Elf_##type
#endif

And that is consistent across the entire codebase

[gAlfonso-bit]

All other changes were done by running clang-tidy and clang-format on the file

[dim]

Hmm in compiler-rt/lib/sanitizer_common/sanitizer_linux_libcdep.cpp it's even defined without any context or comment:

#if !defined(ElfW)
#define ElfW(type) Elf_##type
#endif

libunwind/src/AddressSpace.hpp also has it, but with more explanatory text, and additional typedefs:

#if defined(_LIBUNWIND_USE_DL_ITERATE_PHDR)

// 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.
#if !defined(ElfW)
  #define ElfW(type) Elf_##type
#endif
#if !defined(Elf_Half)
  typedef ElfW(Half) Elf_Half;
#endif
#if !defined(Elf_Phdr)
  typedef ElfW(Phdr) Elf_Phdr;
#endif
#if !defined(Elf_Addr)
  typedef ElfW(Addr) Elf_Addr;
#endif

While I think it's a good stop-gap to define these things locally, at least to get release candidates built, it looks like this is maybe something that we should define in some globally usable LLVM header? @MaskRay do you know if there's a good central ELF-related header that could serve this purpose?

[gAlfonso-bit]

Added context to patch

[MaskRay]

lib/profile/InstrProfilingPort.h. But I think it may be early to move it or generalize the macro for now. NetBSD seems to have ElfW.

[gAlfonso-bit]

In D107493#2932433, @MaskRay wrote:

lib/profile/InstrProfilingPort.h. But I think it may be early to move it or generalize the macro for now. NetBSD seems to have ElfW.

What do we do then? Because this seems wrong

[gAlfonso-bit]

Any updates? Should we try to make the macros consistent or should I just abandon this?

[gAlfonso-bit]

Will revisit this one day.

compiler-rt/lib/profile/InstrProfilingPlatformLinux.c

 /*===- InstrProfilingPlatformLinux.c - Profile data Linux platform ------===*\
 |*
 |* Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 |* See https://llvm.org/LICENSE.txt for license information.
 |* SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 |*
 \*===----------------------------------------------------------------------===*/
 
-#if defined(__linux__) || defined(__FreeBSD__) || defined(__Fuchsia__) || \
+#if defined(__linux__) || defined(__FreeBSD__) || defined(__Fuchsia__) ||      \
     (defined(__sun__) && defined(__svr4__)) || defined(__NetBSD__)
 
 #include <elf.h>
 #include <link.h>
 #include <stdlib.h>
 #include <string.h>
 
 #include "InstrProfiling.h"
 #include "InstrProfilingInternal.h"
 
-#if defined(__FreeBSD__) && !defined(ElfW)
-/*
- * FreeBSD's elf.h and link.h headers do not define the ElfW(type) macro yet.
- * If this is added to all supported FreeBSD versions in the future, this
- * compatibility macro can be removed.
- */
-#define ElfW(type) __ElfN(type)
+#if !defined(ElfW)
+#define ElfW(type) Elf_##type
 #endif
 
 #define PROF_DATA_START INSTR_PROF_SECT_START(INSTR_PROF_DATA_COMMON)
 #define PROF_DATA_STOP INSTR_PROF_SECT_STOP(INSTR_PROF_DATA_COMMON)
 #define PROF_NAME_START INSTR_PROF_SECT_START(INSTR_PROF_NAME_COMMON)
 #define PROF_NAME_STOP INSTR_PROF_SECT_STOP(INSTR_PROF_NAME_COMMON)
 #define PROF_CNTS_START INSTR_PROF_SECT_START(INSTR_PROF_CNTS_COMMON)
 #define PROF_CNTS_STOP INSTR_PROF_SECT_STOP(INSTR_PROF_CNTS_COMMON)

 }
 COMPILER_RT_VISIBILITY uint64_t *__llvm_profile_end_counters(void) {
   return &PROF_CNTS_STOP;
 }
 COMPILER_RT_VISIBILITY uint32_t *__llvm_profile_begin_orderfile(void) {
   return &PROF_ORDERFILE_START;
 }
 
-COMPILER_RT_VISIBILITY ValueProfNode *
-__llvm_profile_begin_vnodes(void) {
+COMPILER_RT_VISIBILITY ValueProfNode *__llvm_profile_begin_vnodes(void) {
   return &PROF_VNODES_START;
 }
 COMPILER_RT_VISIBILITY ValueProfNode *__llvm_profile_end_vnodes(void) {
   return &PROF_VNODES_STOP;
 }
 COMPILER_RT_VISIBILITY ValueProfNode *CurrentVNode = &PROF_VNODES_START;
 COMPILER_RT_VISIBILITY ValueProfNode *EndVNode = &PROF_VNODES_STOP;