Split findUnwindSectionsByPhdr into target-specific functions.

[saugustine]

Summary

This further cleans up the control flow and makes it easier to
optimize and replace portions in a subsequent patch.

This should be NFC, but given the amount of #ifdeffing here,
it may not be. So will watch the buildbots closely.

Also, as this is purely moving existing code around, I plan to
ignore the lint errors.

[saugustine]

I don't know why the linter wants me to indent everything another level. That is clearly not right given the surrounding code.

This file seems to long predate the style guide and lint rules, so most of these reports are not useful.

[jgorbe]

As far as I can tell (there is indeed a lot of ifdeffing going on, please keep an eye on the buildbots) this change seems to be both NFC and an improvement to the previous state, so LGTM.

libunwind/src/AddressSpace.hpp

 // way to handle it. The generalized boolean expression is:
 //
 //  A OR (B AND C) OR (D AND C) OR (B AND E) OR (F AND E) OR (D AND G)
 //
 // Running it through various boolean expression simplifiers gives expressions
 // that don't help at all.
 #elif defined(_LIBUNWIND_ARM_EHABI) || defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
 
-struct _LIBUNWIND_HIDDEN dl_iterate_cb_data {
-  LocalAddressSpace *addressSpace;
-  UnwindInfoSections *sects;
-  uintptr_t targetAddr;
-};
-
-int findUnwindSectionsByPhdr(struct dl_phdr_info *pinfo, size_t, void *data) {
-  auto cbdata = static_cast<dl_iterate_cb_data *>(data);
-  bool found_obj = false;
-  bool found_hdr = false;
-
-  assert(cbdata);
-  assert(cbdata->sects);
-
-  if (cbdata->targetAddr < pinfo->dlpi_addr) {
-    return false;
-  }
-
 #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
 
+static Elf_Addr calculateImageBase(struct dl_phdr_info *pinfo) {
   Elf_Addr image_base = pinfo->dlpi_addr;
-
 #if defined(__ANDROID__) && __ANDROID_API__ < 18
   if (image_base == 0) {
     // Normally, an image base of 0 indicates a non-PIE executable. On
     // versions of Android prior to API 18, the dynamic linker reported a
     // dlpi_addr of 0 for PIE executables. Compute the true image base
     // using the PT_PHDR segment.
     // See https://github.com/android/ndk/issues/505.
     for (Elf_Half i = 0; i < pinfo->dlpi_phnum; i++) {
       const Elf_Phdr *phdr = &pinfo->dlpi_phdr[i];
       if (phdr->p_type == PT_PHDR) {
         image_base = reinterpret_cast<Elf_Addr>(pinfo->dlpi_phdr) -
           phdr->p_vaddr;
         break;
       }
     }
   }
 #endif
+  return image_base;
+}
+
+struct _LIBUNWIND_HIDDEN dl_iterate_cb_data {
+  LocalAddressSpace *addressSpace;
+  UnwindInfoSections *sects;
+  uintptr_t targetAddr;
+};
 
- #if defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
   #if !defined(_LIBUNWIND_SUPPORT_DWARF_INDEX)
     #error "_LIBUNWIND_SUPPORT_DWARF_UNWIND requires _LIBUNWIND_SUPPORT_DWARF_INDEX on this platform."
   #endif
+
+int findUnwindSectionsByPhdr(struct dl_phdr_info *pinfo, size_t, void *data) {
+  auto *cbdata = static_cast<dl_iterate_cb_data *>(data);
+  bool found_obj = false;
+  bool found_hdr = false;
+
+  assert(cbdata);
+  assert(cbdata->sects);
+
+  if (cbdata->targetAddr < pinfo->dlpi_addr)
+    return 0;
+
+  Elf_Addr image_base = calculateImageBase(pinfo);
   size_t object_length;
 
   for (Elf_Half i = 0; i < pinfo->dlpi_phnum; i++) {
     const Elf_Phdr *phdr = &pinfo->dlpi_phdr[i];
     if (phdr->p_type == PT_LOAD) {
       uintptr_t begin = image_base + phdr->p_vaddr;
       uintptr_t end = begin + phdr->p_memsz;
       if (cbdata->targetAddr >= begin && cbdata->targetAddr < end) {
         cbdata->sects->dso_base = begin;
         object_length = phdr->p_memsz;
         found_obj = true;
       }
     } else if (phdr->p_type == PT_GNU_EH_FRAME) {
       EHHeaderParser<LocalAddressSpace>::EHHeaderInfo hdrInfo;
       uintptr_t eh_frame_hdr_start = image_base + phdr->p_vaddr;
       cbdata->sects->dwarf_index_section = eh_frame_hdr_start;
       cbdata->sects->dwarf_index_section_length = phdr->p_memsz;
       found_hdr = EHHeaderParser<LocalAddressSpace>::decodeEHHdr(
           *cbdata->addressSpace, eh_frame_hdr_start, phdr->p_memsz,
           hdrInfo);
       if (found_hdr)
         cbdata->sects->dwarf_section = hdrInfo.eh_frame_ptr;
     }
   }
 
   if (found_obj && found_hdr) {
     cbdata->sects->dwarf_section_length = object_length;
     return true;
   } else {
     return false;
   }
- #else // defined(_LIBUNWIND_ARM_EHABI)
+}
+
+#else  // defined(LIBUNWIND_SUPPORT_DWARF_UNWIND)
+// Given all the #ifdef's above, the code here is for
+// defined(LIBUNWIND_ARM_EHABI)
+
+int findUnwindSectionsByPhdr(struct dl_phdr_info *pinfo, size_t, void *data) {
+  auto *cbdata = static_cast<dl_iterate_cb_data *>(data);
+  bool found_obj = false;
+  bool found_hdr = false;
+
+  assert(cbdata);
+  assert(cbdata->sects);
+
+  if (cbdata->targetAddr < pinfo->dlpi_addr)
+    return 0;
+
+  Elf_Addr image_base = calculateImageBase(pinfo);
+
   for (Elf_Half i = 0; i < pinfo->dlpi_phnum; i++) {
     const Elf_Phdr *phdr = &pinfo->dlpi_phdr[i];
     if (phdr->p_type == PT_LOAD) {
       uintptr_t begin = image_base + phdr->p_vaddr;
       uintptr_t end = begin + phdr->p_memsz;
       if (cbdata->targetAddr >= begin && cbdata->targetAddr < end)
         found_obj = true;
     } else if (phdr->p_type == PT_ARM_EXIDX) {
       uintptr_t exidx_start = image_base + phdr->p_vaddr;
       cbdata->sects->arm_section = exidx_start;
       cbdata->sects->arm_section_length = phdr->p_memsz;
       found_hdr = true;
     }
   }
   return found_obj && found_hdr;
- #endif
 }
+#endif  // defined(LIBUNWIND_SUPPORT_DWARF_UNWIND)
 #endif  // defined(_LIBUNWIND_ARM_EHABI) || defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
 
 
 inline bool LocalAddressSpace::findUnwindSections(pint_t targetAddr,
                                                   UnwindInfoSections &info) {
 #ifdef __APPLE__
   dyld_unwind_sections dyldInfo;
   if (_dyld_find_unwind_sections((void *)targetAddr, &dyldInfo)) {