fix: symbols / sections followups

.github/workflows/CI.yml

@@ -8,6 +8,7 @@ on:
       - include/*
       - tests/*
       - src/*
+      - example/*
 
   pull_request:
     paths:
@@ -16,6 +17,7 @@ on:
       - include/*
       - tests/*
       - src/*
+      - example/*
 
 defaults:
   run:
@@ -38,6 +40,37 @@ jobs:
       - name: Check formatting
         run: find src include tests -name '*.cpp' -o -name '*.hpp' | xargs clang-format --dry-run --Werror
 
+  example:
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, macos-latest, windows-latest]
+
+    name: example / ${{ matrix.os }}
+    runs-on: ${{ matrix.os }}
+
+    steps:
+      - uses: actions/checkout@v4
+
+      # FETCHCONTENT_SOURCE_DIR_DYLIB makes FetchContent use the checked out
+      # sources instead of the released tag, so that the example is built
+      # against the code of the current branch.
+      - name: Generate project files
+        run: cmake example -B example/build -DFETCHCONTENT_SOURCE_DIR_DYLIB="${{ github.workspace }}"
+
+      - name: Build example
+        run: cmake --build example/build --config Release
+
+      # Multi config generators place the binaries in a per config subdirectory,
+      # and the example loads its dynamic library from the working directory.
+      - name: Run example
+        working-directory: example/build
+        run: |
+          if [ -d Release ]; then
+            cd Release
+          fi
+          ./dylib_example
+
   windows_msvc:
     strategy:
       fail-fast: false

CMakeLists.txt

@@ -1,6 +1,18 @@
 cmake_minimum_required(VERSION 3.11...3.31)
 
-project(dylib VERSION 3.0.1 LANGUAGES CXX)
+file(READ "${CMAKE_CURRENT_SOURCE_DIR}/include/dylib.hpp" DYLIB_HEADER)
+
+foreach(part MAJOR MINOR PATCH)
+    if(NOT DYLIB_HEADER MATCHES "#define DYLIB_VERSION_${part} ([0-9]+)")
+        message(FATAL_ERROR "Could not parse DYLIB_VERSION_${part} from include/dylib.hpp")
+    endif()
+    set(DYLIB_VERSION_${part} ${CMAKE_MATCH_1})
+endforeach()
+
+project(dylib
+    VERSION ${DYLIB_VERSION_MAJOR}.${DYLIB_VERSION_MINOR}.${DYLIB_VERSION_PATCH}
+    LANGUAGES CXX
+)
 
 include(GNUInstallDirs)
 

README.md

@@ -1,6 +1,6 @@
 # dylib
 
-[![version](https://img.shields.io/badge/Version-3.0.1-blue.svg)](https://github.com/martin-olivier/dylib/releases/tag/v3.0.1)
+[![version](https://img.shields.io/badge/Version-3.1.0-blue.svg)](https://github.com/martin-olivier/dylib/releases/tag/v3.1.0)
 [![license](https://img.shields.io/badge/License-MIT-orange.svg)](https://github.com/martin-olivier/dylib/blob/main/LICENSE)
 [![cpp](https://img.shields.io/badge/Compatibility-C++11-darkgreen.svg)](https://isocpp.org)
 [![ci](https://github.com/martin-olivier/dylib/actions/workflows/CI.yml/badge.svg)](https://github.com/martin-olivier/dylib/actions/workflows/CI.yml)
@@ -28,7 +28,7 @@ vcpkg install dylib
 ```
 
 ```sh
-conan install --requires=dylib/3.0.1
+conan install --requires=dylib/3.1.0
 ```
 
 ### Using CMake Fetch
@@ -41,7 +41,7 @@ include(FetchContent)
 FetchContent_Declare(
     dylib
     GIT_REPOSITORY "https://github.com/martin-olivier/dylib"
-    GIT_TAG        "v3.0.1"
+    GIT_TAG        "v3.1.0"
 )
 
 FetchContent_MakeAvailable(dylib)
@@ -219,6 +219,17 @@ try {
 }
 ```
 
+### Version
+
+`dylib.hpp` exposes its version as macros, which lets you detect the availability of a feature at compile time:
+
+```c++
+#if DYLIB_VERSION_MAJOR > 3 || (DYLIB_VERSION_MAJOR == 3 && DYLIB_VERSION_MINOR >= 1)
+    for (auto &section : lib.sections())
+        std::cout << section << std::endl;
+#endif
+```
+
 ## Example
 
 A full example about the usage of the `dylib` library is available [HERE](example)

example/CMakeLists.txt

@@ -15,7 +15,7 @@ include(FetchContent)
 FetchContent_Declare(
     dylib
     GIT_REPOSITORY  "https://github.com/martin-olivier/dylib"
-    GIT_TAG         "v3.0.1"
+    GIT_TAG         "v3.1.0"
 )
 
 FetchContent_MakeAvailable(dylib)

example/README.md

@@ -34,7 +34,7 @@ You will have the following result:
 
 ```sh
 Hello World!
-dylib - v3.0.1
+dylib - v3.1.0
 pi value: 3.14159
 magic value: cafebabe
 10 + 10 = 20

example/lib.cpp

@@ -26,7 +26,7 @@ namespace example {
 
     namespace dylib {
         LIB_EXPORT std::string info() {
-            return "dylib - v3.0.1";
+            return "dylib - v3.1.0";
         }
     }
 

include/dylib.hpp

@@ -1,6 +1,6 @@
 /**
  * @file dylib.hpp
- * @version 3.0.1
+ * @version 3.1.0
  * @brief C++ cross-platform wrapper around dynamic loading of shared libraries
  * @link https://github.com/martin-olivier/dylib
  *
@@ -12,6 +12,21 @@
 
 #pragma once
 
+#define DYLIB_VERSION_MAJOR 3
+#define DYLIB_VERSION_MINOR 1
+#define DYLIB_VERSION_PATCH 0
+
+#ifdef _WIN32
+#define DYLIB_WIN_MAC_OTHER(win_def, mac_def, other_def) win_def
+#define DYLIB_WIN_OTHER(win_def, other_def) win_def
+#elif defined(__APPLE__)
+#define DYLIB_WIN_MAC_OTHER(win_def, mac_def, other_def) mac_def
+#define DYLIB_WIN_OTHER(win_def, other_def) other_def
+#else
+#define DYLIB_WIN_MAC_OTHER(win_def, mac_def, other_def) other_def
+#define DYLIB_WIN_OTHER(win_def, other_def) other_def
+#endif
+
 #include <cstdint>
 #include <stdexcept>
 #include <string>
@@ -42,17 +57,6 @@
 #endif
 #endif
 
-#ifdef _WIN32
-#define DYLIB_WIN_MAC_OTHER(win_def, mac_def, other_def) win_def
-#define DYLIB_WIN_OTHER(win_def, other_def) win_def
-#elif defined(__APPLE__)
-#define DYLIB_WIN_MAC_OTHER(win_def, mac_def, other_def) mac_def
-#define DYLIB_WIN_OTHER(win_def, other_def) other_def
-#else
-#define DYLIB_WIN_MAC_OTHER(win_def, mac_def, other_def) other_def
-#define DYLIB_WIN_OTHER(win_def, other_def) other_def
-#endif
-
 namespace dylib {
 
 using native_handle_type = DYLIB_WIN_OTHER(HINSTANCE, void *);
@@ -316,12 +320,12 @@ class library {
     /**
      *  @return the dynamic library handle
      */
-    native_handle_type native_handle() noexcept;
+    native_handle_type native_handle() const noexcept;
 
 protected:
     native_handle_type m_handle{nullptr};
 #ifndef _WIN32
-    int m_fd{-1};
+    std::string m_path;
 #endif
 };
 

src/dylib.cpp

@@ -42,7 +42,6 @@ struct internal_symbol_info {
 
 std::vector<internal_symbol_info> get_symbols(native_handle_type handle, int fd);
 std::vector<std::string> get_sections(native_handle_type handle, int fd);
-std::string demangle_symbol(const char *symbol);
 
 static native_handle_type open_lib(const char *path) noexcept {
 #ifdef _WIN32
@@ -90,18 +89,42 @@ static std::string get_error_description() noexcept {
 #endif
 }
 
+#ifndef _WIN32
+class scoped_fd {
+public:
+    explicit scoped_fd(const std::string &path) : m_fd(open(path.c_str(), O_RDONLY)) {
+        if (m_fd < 0)
+            throw std::runtime_error("Could not open file '" + path + "': " + strerror(errno));
+    }
+
+    scoped_fd(const scoped_fd &) = delete;
+    scoped_fd &operator=(const scoped_fd &) = delete;
+
+    ~scoped_fd() {
+        close(m_fd);
+    }
+
+    int get() const noexcept {
+        return m_fd;
+    }
+
+private:
+    int m_fd;
+};
+#endif
+
 library::library(library &&other) noexcept {
     std::swap(m_handle, other.m_handle);
 #ifndef _WIN32
-    std::swap(m_fd, other.m_fd);
+    std::swap(m_path, other.m_path);
 #endif
 }
 
 library &library::operator=(library &&other) noexcept {
     if (this != &other) {
         std::swap(m_handle, other.m_handle);
 #ifndef _WIN32
-        std::swap(m_fd, other.m_fd);
+        std::swap(m_path, other.m_path);
 #endif
     }
     return *this;
@@ -141,9 +164,7 @@ library::library(const char *lib_path, dylib::decorations decorations) {
         throw load_error("Could not load library '" + lib + "':\n" + get_error_description());
 
 #ifndef _WIN32
-    m_fd = open(lib.c_str(), O_RDONLY);
-    if (m_fd < 0)
-        throw load_error("Could not open file '" + lib + "':\n" + strerror(errno));
+    m_path = lib;
 #endif
 }
 
@@ -158,10 +179,6 @@ library::library(const std::filesystem::path &lib_path, decorations decorations)
 library::~library() {
     if (m_handle)
         close_lib(m_handle);
-#ifndef _WIN32
-    if (m_fd > -1)
-        close(m_fd);
-#endif
 }
 
 native_symbol_type library::get_symbol(const char *symbol_name) const {
@@ -186,10 +203,14 @@ native_symbol_type library::get_symbol(const char *symbol_name) const {
     initial_error = get_error_description();
 
     for (const auto &sym : symbols()) {
-        if (!sym.loadable)
+        /*
+         * Only C++ symbols are considered here: a C symbol is not mangled, so it would
+         * already have been resolved by the locate_symbol call above.
+         */
+        if (!sym.loadable || sym.type != symbol_type::CPP)
             continue;
 
-        std::string demangled = demangle_symbol(sym.name.c_str());
+        const std::string &demangled = sym.demangled_name;
 
         if (demangled.find(symbol_name) == 0 &&
             (demangled.size() == symbol_name_len || demangled[symbol_name_len] == '('))
@@ -215,7 +236,7 @@ native_symbol_type library::get_symbol(const std::string &symbol_name) const {
     return get_symbol(symbol_name.c_str());
 }
 
-native_handle_type library::native_handle() noexcept {
+native_handle_type library::native_handle() const noexcept {
     return m_handle;
 }
 
@@ -227,7 +248,13 @@ std::vector<symbol_info> library::symbols() const {
         throw std::logic_error("Attempted to use a moved library object");
 
     try {
-        internal_symbols = get_symbols(m_handle, DYLIB_WIN_MAC_OTHER(-1, m_fd, -1));
+#ifdef __APPLE__
+        scoped_fd fd(m_path);
+
+        internal_symbols = get_symbols(m_handle, fd.get());
+#else
+        internal_symbols = get_symbols(m_handle, -1);
+#endif
 
         symbols.reserve(internal_symbols.size());
 
@@ -251,7 +278,13 @@ std::vector<std::string> library::sections() const {
         throw std::logic_error("Attempted to use a moved library object");
 
     try {
-        return get_sections(m_handle, DYLIB_WIN_MAC_OTHER(-1, m_fd, m_fd));
+#ifdef _WIN32
+        return get_sections(m_handle, -1);
+#else
+        scoped_fd fd(m_path);
+
+        return get_sections(m_handle, fd.get());
+#endif
     } catch (const std::runtime_error &e) {
         throw section_collection_error(e.what());
     }

src/symbols.cpp

@@ -385,13 +385,24 @@ std::vector<internal_symbol_info> get_symbols(void *handle, int fd) {
     if (!symtab || !strtab || symentries == 0)
         return symbols_list;
 
-    size = strtab - (char *)symtab;
+    /*
+     * The dynamic section does not record the size of the symbol table, so it is
+     * deduced from the fact that the string table usually directly follows it.
+     * Bail out instead of underflowing if a linker lays them out the other way.
+     */
+    if (strtab <= (const char *)symtab)
+        return symbols_list;
+
+    size = (unsigned long)(strtab - (char *)symtab);
 
-    for (int i = 0; i < size / symentries; ++i) {
-        ElfSym *sym = &symtab[i];
+    for (unsigned long i = 0; i < size / symentries; ++i) {
+        unsigned char type = DYLIB_ELF_ST_TYPE(symtab[i].st_info);
 
-        if (DYLIB_ELF_ST_TYPE(symtab[i].st_info) == STT_FUNC) {
-            const char *name = &strtab[sym->st_name];
+        /*
+         * Collect functions (STT_FUNC) and global variables (STT_OBJECT)
+         */
+        if (type == STT_FUNC || type == STT_OBJECT) {
+            const char *name = &strtab[symtab[i].st_name];
 
             add_symbol(symbols_list, name, !!dlsym(handle, name));
         }

tests/lib.cpp

@@ -44,6 +44,8 @@ LIB_EXPORT void list_add_string(std::vector<std::string> &cont, std::string elem
 }
 
 namespace tools {
+LIB_EXPORT double pi_value = 3.14159;
+
 LIB_EXPORT double adder() {
     return 0;
 }