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Fix #954. safe_memcmp in tinystring. #966

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Fix #954. safe_memcmp in tinystring. #966

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13 changes: 13 additions & 0 deletions src/tools.h
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Original file line number Diff line number Diff line change
Expand Up @@ -22,6 +22,8 @@
#ifndef OPENZIM_LIBZIM_TOOLS_H
#define OPENZIM_LIBZIM_TOOLS_H

#include <cstddef> // size_t
#include <cstring> // memcmp
#include <string>
#include <tuple>
#include <map>
Expand Down Expand Up @@ -71,6 +73,17 @@ namespace zim {
return count;
}

// Work around for errors reported by too picky UB sanitizer tools on std::memcmp()
// being called with a nullptr pointer argument even though count==0. Explicit
// nullptr checks to satisfy other picky compilers.
template <typename T>
int safe_memcmp(T const *const lhs, T const *const rhs, std::size_t count) noexcept {
if(count == 0UL || lhs == nullptr || rhs == nullptr) {
return 0;
}
return std::memcmp(lhs, rhs, count);
}

namespace writer {
class Dirent;
bool isFrontArticle(const Dirent* dirent, const Hints& hints);
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7 changes: 4 additions & 3 deletions src/writer/tinyString.h
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Original file line number Diff line number Diff line change
Expand Up @@ -20,6 +20,7 @@
#ifndef ZIM_WRITER_TINYSTRING_H
#define ZIM_WRITER_TINYSTRING_H

#include "../tools.h"
#include "../zim_types.h"
#include <cstring>

Expand Down Expand Up @@ -66,11 +67,11 @@ namespace zim
size_t size() const { return m_size; }
const char* const data() const { return m_data; }
bool operator==(const TinyString& other) const {
return (m_size == other.m_size) && (std::memcmp(m_data, other.m_data, m_size) == 0);
return (m_size == other.m_size) && (safe_memcmp(m_data, other.m_data, m_size) == 0);
}
bool operator<(const TinyString& other) const {
auto min_size = std::min(m_size, other.m_size);
auto ret = std::memcmp(m_data, other.m_data, min_size);
const auto min_size = std::min(m_size, other.m_size);
const auto ret = safe_memcmp(m_data, other.m_data, min_size);
if (ret == 0) {
return m_size < other.m_size;
} else {
Expand Down