From 63af0cd7523b66327cda4318c8e607d5cf3ca39d Mon Sep 17 00:00:00 2001
From: Zequan Wu <zequanwu@google.com>
Date: Thu, 15 Dec 2022 12:27:22 +0800
Subject: [PATCH] Cleanup strncmp and use string_view in elf_reader.cc.

Change-Id: I74c755f1ade80bb4313e4fd14e5dc6bab419a0a6
Reviewed-on: https://chromium-review.googlesource.com/c/breakpad/breakpad/+/4099505
Reviewed-by: Mark Mentovai <mark@chromium.org>
---
 src/common/dwarf/elf_reader.cc | 36 ++++++++++++++++++++++------------
 src/common/dwarf/elf_reader.h  |  4 +++-
 2 files changed, 27 insertions(+), 13 deletions(-)

diff --git a/src/common/dwarf/elf_reader.cc b/src/common/dwarf/elf_reader.cc
index 5fd1cfb9..7664377c 100644
--- a/src/common/dwarf/elf_reader.cc
+++ b/src/common/dwarf/elf_reader.cc
@@ -39,9 +39,9 @@
 #include <unistd.h>
 
 #include <algorithm>
-#include <cstring>
 #include <map>
 #include <string>
+#include <string_view>
 #include <vector>
 // TODO(saugustine): Add support for compressed debug.
 // Also need to add configure tests for zlib.
@@ -107,6 +107,12 @@ const int kAARCH64PLT0Size = 0x20;
 // Suffix for PLT functions when it needs to be explicitly identified as such.
 const char kPLTFunctionSuffix[] = "@plt";
 
+// Replace callsites of this function to std::string_view::starts_with after
+// adopting C++20.
+bool StringViewStartsWith(std::string_view sv, std::string_view prefix) {
+  return sv.compare(0, prefix.size(), prefix) == 0;
+}
+
 }  // namespace
 
 namespace google_breakpad {
@@ -215,7 +221,7 @@ class ElfSectionReader {
                 (header_.sh_offset - offset_aligned);
 
     // Check for and handle any compressed contents.
-    //if (name == ".zdebug_")
+    //if (StringViewStartsWith(name, ".zdebug_"))
     //  DecompressZlibContents();
     // TODO(saugustine): Add support for proposed elf-section flag
     // "SHF_COMPRESS".
@@ -359,8 +365,8 @@ class ElfReaderImpl {
       // "opd_section_" must always be checked for NULL before use.
       opd_section_ = GetSectionInfoByName(".opd", &opd_info_);
       for (unsigned int k = 0u; k < GetNumSections(); ++k) {
-        const char* name = GetSectionName(section_headers_[k].sh_name);
-        if (strncmp(name, ".text", strlen(".text")) == 0) {
+        std::string_view name{GetSectionName(section_headers_[k].sh_name)};
+        if (StringViewStartsWith(name, ".text")) {
           base_for_text_ =
               section_headers_[k].sh_addr - section_headers_[k].sh_offset;
           break;
@@ -809,9 +815,11 @@ class ElfReaderImpl {
     // Debug sections are likely to be near the end, so reverse the
     // direction of iteration.
     for (int k = GetNumSections() - 1; k >= 0; --k) {
-      const char* name = GetSectionName(section_headers_[k].sh_name);
-      if (strncmp(name, ".debug", strlen(".debug")) == 0) return true;
-      if (strncmp(name, ".zdebug", strlen(".zdebug")) == 0) return true;
+      std::string_view name{GetSectionName(section_headers_[k].sh_name)};
+      if (StringViewStartsWith(name, ".debug") ||
+          StringViewStartsWith(name, ".zdebug")) {
+        return true;
+      }
     }
     return false;
   }
@@ -1213,11 +1221,15 @@ const char* ElfReader::GetSectionInfoByName(const string& section_name,
   }
 }
 
-bool ElfReader::SectionNamesMatch(const string& name, const string& sh_name) {
-  if ((name.find(".debug_", 0) == 0) && (sh_name.find(".zdebug_", 0) == 0)) {
-    const string name_suffix(name, strlen(".debug_"));
-    const string sh_name_suffix(sh_name, strlen(".zdebug_"));
-    return name_suffix == sh_name_suffix;
+bool ElfReader::SectionNamesMatch(std::string_view name,
+                                  std::string_view sh_name) {
+  std::string_view debug_prefix{".debug_"};
+  std::string_view zdebug_prefix{".zdebug_"};
+  if (StringViewStartsWith(name, debug_prefix) &&
+      StringViewStartsWith(sh_name, zdebug_prefix)) {
+    name.remove_prefix(debug_prefix.length());
+    sh_name.remove_prefix(zdebug_prefix.length());
+    return name == sh_name;
   }
   return name == sh_name;
 }
diff --git a/src/common/dwarf/elf_reader.h b/src/common/dwarf/elf_reader.h
index 672969d8..a6dec755 100644
--- a/src/common/dwarf/elf_reader.h
+++ b/src/common/dwarf/elf_reader.h
@@ -16,6 +16,7 @@
 #define COMMON_DWARF_ELF_READER_H__
 
 #include <string>
+#include <string_view>
 #include <vector>
 
 #include "common/dwarf/types.h"
@@ -145,7 +146,8 @@ class ElfReader {
   // appears in the elf-file, adjusting for compressed debug section
   // names.  For example, returns true if name == ".debug_abbrev" and
   // sh_name == ".zdebug_abbrev"
-  static bool SectionNamesMatch(const string& name, const string& sh_name);
+  static bool SectionNamesMatch(std::string_view name,
+                                std::string_view sh_name);
 
  private:
   // Lazily initialize impl32_ and return it.