[Courgette] Clean up Disassembler; fix ELF Memory leaks.

courgette/rel32_finder_win32_x86.cc

Index: courgette/rel32_finder_win32_x86.cc
diff --git a/courgette/rel32_finder_win32_x86.cc b/courgette/rel32_finder_win32_x86.cc
index 171b781ba707f2e8dc389d1c0ea7b17a6cc74ea2..44e991dd6c917e0c73d181f2fbe6d9c33f736bbd 100644
--- a/courgette/rel32_finder_win32_x86.cc
+++ b/courgette/rel32_finder_win32_x86.cc
@@ -9,10 +9,9 @@
 namespace courgette {
 
 Rel32FinderWin32X86::Rel32FinderWin32X86(
-    RVA relocs_start_rva, RVA relocs_end_rva, RVA image_end_rva)
+    RVA relocs_start_rva, RVA relocs_end_rva)
     : relocs_start_rva_(relocs_start_rva),
-      relocs_end_rva_(relocs_end_rva),
-      image_end_rva_(image_end_rva) {
+      relocs_end_rva_(relocs_end_rva) {
 }
 
 Rel32FinderWin32X86::~Rel32FinderWin32X86() {
@@ -30,7 +29,8 @@ void Rel32FinderWin32X86::SwapRel32TargetRVAs(std::map<RVA, int>* dest) {
 
 Rel32FinderWin32X86_Basic::Rel32FinderWin32X86_Basic(
     RVA relocs_start_rva, RVA relocs_end_rva, RVA image_end_rva)
-    : Rel32FinderWin32X86(relocs_start_rva, relocs_end_rva, image_end_rva) {
+    : Rel32FinderWin32X86(relocs_start_rva, relocs_end_rva),
+      image_end_rva_(image_end_rva) {
 }
 
 Rel32FinderWin32X86_Basic::~Rel32FinderWin32X86_Basic() {
@@ -51,6 +51,10 @@ void Rel32FinderWin32X86_Basic::Find(const uint8_t* start_pointer,
   const uint8_t* p = start_pointer;
   while (p < end_pointer) {
     RVA current_rva = static_cast<RVA>(p - adjust_pointer_to_rva);
+
+    // Skip the base reloation table if we encounter it.
+    // Note: We're not bothering to handle the edge case where a Rel32 pointer
+    // collides with |relocs_start_rva_| by being {1, 2, 3}-bytes before it.
     if (current_rva == relocs_start_rva_) {
       if (relocs_start_rva_ < relocs_end_rva_) {
         p += relocs_end_rva_ - relocs_start_rva_;
@@ -58,13 +62,10 @@ void Rel32FinderWin32X86_Basic::Find(const uint8_t* start_pointer,
       }
     }
 
-    //while (abs32_pos != abs32_locations.end() && *abs32_pos < current_rva)
-    //  ++abs32_pos;
-
     // Heuristic discovery of rel32 locations in instruction stream: are the
     // next few bytes the start of an instruction containing a rel32
     // addressing mode?
-    const uint8_t* rel32 = NULL;
+    const uint8_t* rel32 = nullptr;
 
     if (p + 5 <= end_pointer) {
       if (*p == 0xE8 || *p == 0xE9) {  // jmp rel32 and call rel32
@@ -95,9 +96,8 @@ void Rel32FinderWin32X86_Basic::Find(const uint8_t* start_pointer,
       }
 
       RVA target_rva = rel32_rva + 4 + Read32LittleEndian(rel32);
-      // To be valid, rel32 target must be within image, and within this
-      // section.
-      if (IsValidRVA(target_rva) &&
+      // Valid, rel32 target must be within image, and within this section.
+      if (target_rva < image_end_rva_ &&  // Subsumes rva != kUnassignedRVA.
           start_rva <= target_rva && target_rva < end_rva) {

[grt (UTC plus 2), 2016/02/11 16:55:34]

is it valid for end_rva to be > image_end_rva_? can this be simplified to
"target_rva < end_rva && target_rva >= start_rva"?

[huangs, 2016/02/12 01:08:42]

The original code intends to separate the "is RVA valid" and "is RVA in range"
semantics, but I suppose this is weak enough to be overridden by non-redundancy.

Note that this renders |image_end_rva_| useless.  I'll do this removal of
|image_end_rva_| (also from tests) in a follow-up patch.

         rel32_locations_.push_back(rel32_rva);
 #if COURGETTE_HISTOGRAM_TARGETS