Fix tautological-constant-out-of-range-compare with Clang on macOS

PiperOrigin-RevId: 373424469 Change-Id: Ia6e89e1872f98adc5f1c1b36a601df8d351080ab
google · May 12, 2021 · 6a21a82 · 6a21a82
1 parent 933e158
commit 6a21a82
Show file tree

Hide file tree

Showing 3 changed files with 21 additions and 14 deletions.
diff --git a/ida/flow_analysis.cc b/ida/flow_analysis.cc
@@ -366,9 +366,7 @@ void AnalyzeFlowIda(EntryPoints* entry_points, const ModuleMap& modules,
     if (mark_x86_nops) {
       // FLAG_NOP is only important when reconstructing functions, thus we can
       // set if after AnalyzeFlow().
-      const auto& new_instruction_bytes = new_instruction.GetBytes();
-      new_instruction.SetFlag(FLAG_NOP, IsNopX86(new_instruction_bytes.data(),
-                                                 new_instruction_bytes.size()));
+      new_instruction.SetFlag(FLAG_NOP, IsNopX86(new_instruction.GetBytes()));
     }
 
     instructions->push_back(new_instruction);

diff --git a/x86_nop.cc b/x86_nop.cc
@@ -14,7 +14,12 @@
 
 #include "third_party/zynamics/binexport/x86_nop.h"
 
-bool IsNopX86(const char* m, size_t size) {
+#include <cstdint>
+
+bool IsNopX86(absl::string_view bytes) {
+  auto* m = reinterpret_cast<const uint8_t*>(bytes.data());
+  size_t size = bytes.size();
+
   // Consume up to six prefix bytes:
   for (int i = 6; i > 0 && size > 0 && m[0] == 0x66; --i, --size, ++m) {
   }
@@ -52,7 +57,8 @@ bool IsNopX86(const char* m, size_t size) {
       if (m[1] == 0x74) {
         if (m[2] == 0x00) {
           return true;  // 8d 74 00 lea esi, esi
-        } else if (m[2] == 0x26) {
+        }
+        if (m[2] == 0x26) {
           if (size >= 4 && m[3] == 0x00) {
             return true;  // 8d 74 26 00 lea esi, [esi + eiz * 1 + 0]
           }
@@ -64,8 +70,9 @@ bool IsNopX86(const char* m, size_t size) {
         if (m[1] == 0xb4) {
           if (m[2] == 0x00 && m[3] == 0x00) {
             return true;  // 8d b4 00 00 lea
-          } else if (size >= 7 && m[2] == 0x26 && m[3] == 0x00 &&
-                     m[4] == 0x00 && m[5] == 0x00 && m[6] == 0x00) {
+          }
+          if (size >= 7 && m[2] == 0x26 && m[3] == 0x00 && m[4] == 0x00 &&
+              m[5] == 0x00 && m[6] == 0x00) {
             return true;  // 8d b4 26 00 00 00 00 lea
           }
         } else if (m[1] == 0xbd && m[2] == 0x00 && m[3] == 0x00) {
@@ -75,8 +82,9 @@ bool IsNopX86(const char* m, size_t size) {
           if (m[1] == 0xb6 && m[2] == 0x00 && m[3] == 0x00 && m[4] == 0x00 &&
               m[5] == 0x00) {
             return true;  // 8d b6 00 00 00 00 lea
-          } else if (m[1] == 0xbf && m[2] == 0x00 && m[3] == 0x00 &&
-                     m[4] == 0x00 && m[5] == 0x00) {
+          }
+          if (m[1] == 0xbf && m[2] == 0x00 && m[3] == 0x00 && m[4] == 0x00 &&
+              m[5] == 0x00) {
             return true;  // 8d bf 00 00 00 00 lea
           }
           if (size >= 7 && m[1] == 0xbc && m[2] == 0x27 && m[3] == 0x00 &&
@@ -95,4 +103,3 @@ bool IsNopX86(const char* m, size_t size) {
   }
   return false;
 }
-
diff --git a/x86_nop.h b/x86_nop.h
@@ -17,10 +17,12 @@
 
 #include <cstddef>
 
-// Returns true if the instruction starting at "memory" (which contains at least
-// "size" bytes) is a NOP instruction. NOPs have been taken from the GNU
-// assembler tc-i386.c i386_align_code().
+#include "third_party/absl/strings/string_view.h"
+
+// Returns true if the instruction starting at the first byte in "bytes" is a
+// NOP instruction. NOPs have been taken from the GNU assembler
+// i386_align_code() (in tc-i386.c).
 // For details, see b/24084521#comment7
-bool IsNopX86(const char* m, size_t size);
+bool IsNopX86(absl::string_view bytes);
 
 #endif  // X86_NOP_H_