Coverage Report

Created: 2025-06-22 06:59

/src/gdal/port/cplgetsymbol.cpp
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/******************************************************************************
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 *
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 * Project:  Common Portability Library
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 * Purpose:  Fetch a function pointer from a shared library / DLL.
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 * Author:   Frank Warmerdam, warmerdam@pobox.com
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 *
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 ******************************************************************************
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 * Copyright (c) 1999, Frank Warmerdam
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 * Copyright (c) 2009-2013, Even Rouault <even dot rouault at spatialys.com>
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 *
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 * SPDX-License-Identifier: MIT
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 ****************************************************************************/
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#include "cpl_port.h"
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#include "cpl_conv.h"
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#include <cstddef>
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#include "cpl_config.h"
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#include "cpl_error.h"
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#include "cpl_string.h"
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/* ==================================================================== */
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/*                  Unix Implementation                                 */
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/* ==================================================================== */
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/* MinGW32 might define HAVE_DLFCN_H, so skip the unix implementation */
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#if defined(HAVE_DLFCN_H) && !defined(_WIN32)
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#define GOT_GETSYMBOL
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#include <dlfcn.h>
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#include <map>
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#include <mutex>
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/************************************************************************/
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/*                            CPLGetSymbol()                            */
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/************************************************************************/
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/**
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 * Fetch a function pointer from a shared library / DLL.
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 *
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 * This function is meant to abstract access to shared libraries and
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 * DLLs and performs functions similar to dlopen()/dlsym() on Unix and
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 * LoadLibrary() / GetProcAddress() on Windows.
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 *
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 * If no support for loading entry points from a shared library is available
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 * this function will always return NULL.   Rules on when this function
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 * issues a CPLError() or not are not currently well defined, and will have
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 * to be resolved in the future.
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 *
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 * Currently CPLGetSymbol() doesn't try to:
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 * <ul>
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 *  <li> prevent the reference count on the library from going up
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 *    for every request, or given any opportunity to unload
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 *    the library.
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 *  <li> Attempt to look for the library in non-standard
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 *    locations.
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 *  <li> Attempt to try variations on the symbol name, like
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 *    pre-pending or post-pending an underscore.
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 * </ul>
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 *
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 * Some of these issues may be worked on in the future.
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 *
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 * @param pszLibrary the name of the shared library or DLL containing
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 * the function.  May contain path to file.  If not system supplies search
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 * paths will be used.
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 * @param pszSymbolName the name of the function to fetch a pointer to.
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 * @return A pointer to the function if found, or NULL if the function isn't
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 * found, or the shared library can't be loaded.
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 */
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void *CPLGetSymbol(const char *pszLibrary, const char *pszSymbolName)
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{
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    static std::mutex mutex;
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    static std::map<std::string, void *> mapLibraryNameToHandle;
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    std::lock_guard oLock(mutex);
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    void *pLibrary;
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    const char *pszNonNullLibrary = pszLibrary ? pszLibrary : "";
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    auto oIter = mapLibraryNameToHandle.find(pszNonNullLibrary);
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    if (oIter == mapLibraryNameToHandle.end())
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    {
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        pLibrary = dlopen(pszLibrary, RTLD_LAZY);
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        if (pLibrary == nullptr)
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        {
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            CPLError(CE_Failure, CPLE_AppDefined, "%s", dlerror());
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            return nullptr;
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        }
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        mapLibraryNameToHandle[pszNonNullLibrary] = pLibrary;
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    }
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    else
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    {
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        pLibrary = oIter->second;
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    }
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    void *pSymbol = dlsym(pLibrary, pszSymbolName);
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#if (defined(__APPLE__) && defined(__MACH__))
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    /* On mach-o systems, C symbols have a leading underscore and depending
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     * on how dlcompat is configured it may or may not add the leading
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     * underscore.  If dlsym() fails, add an underscore and try again.
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     */
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    if (pSymbol == nullptr)
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    {
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        char withUnder[256] = {};
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        snprintf(withUnder, sizeof(withUnder), "_%s", pszSymbolName);
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        pSymbol = dlsym(pLibrary, withUnder);
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    }
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#endif
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    if (pSymbol == nullptr)
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    {
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        CPLError(CE_Failure, CPLE_AppDefined, "%s", dlerror());
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        return nullptr;
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    }
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    return (pSymbol);
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}
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#endif /* def __unix__ && defined(HAVE_DLFCN_H) */
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/* ==================================================================== */
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/*                 Windows Implementation                               */
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/* ==================================================================== */
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#if defined(_WIN32)
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#define GOT_GETSYMBOL
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#include <windows.h>
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/************************************************************************/
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/*                            CPLGetSymbol()                            */
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/************************************************************************/
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void *CPLGetSymbol(const char *pszLibrary, const char *pszSymbolName)
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{
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    void *pLibrary = nullptr;
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    void *pSymbol = nullptr;
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    // Avoid error boxes to pop up (#5211, #5525).
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    UINT uOldErrorMode =
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        SetErrorMode(SEM_NOOPENFILEERRORBOX | SEM_FAILCRITICALERRORS);
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#if defined(_MSC_VER) || __MSVCRT_VERSION__ >= 0x0601
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    if (CPLTestBool(CPLGetConfigOption("GDAL_FILENAME_IS_UTF8", "YES")))
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    {
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        wchar_t *pwszFilename =
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            CPLRecodeToWChar(pszLibrary, CPL_ENC_UTF8, CPL_ENC_UCS2);
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        pLibrary = LoadLibraryW(pwszFilename);
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        CPLFree(pwszFilename);
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    }
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    else
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#endif
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    {
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        pLibrary = LoadLibraryA(pszLibrary);
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    }
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    if (pLibrary <= (void *)HINSTANCE_ERROR)
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    {
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        LPVOID lpMsgBuf = nullptr;
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        int nLastError = GetLastError();
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        // Restore old error mode.
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        SetErrorMode(uOldErrorMode);
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        FormatMessage(
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            FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM |
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                FORMAT_MESSAGE_IGNORE_INSERTS,
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            nullptr, nLastError, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
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            reinterpret_cast<LPTSTR>(&lpMsgBuf), 0, nullptr);
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        CPLError(CE_Failure, CPLE_AppDefined,
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                 "Can't load requested DLL: %s\n%d: %s", pszLibrary, nLastError,
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                 static_cast<const char *>(lpMsgBuf));
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        return nullptr;
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    }
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    // Restore old error mode.
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    SetErrorMode(uOldErrorMode);
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    pSymbol = reinterpret_cast<void *>(
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        GetProcAddress(static_cast<HINSTANCE>(pLibrary), pszSymbolName));
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    if (pSymbol == nullptr)
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    {
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        CPLError(CE_Failure, CPLE_AppDefined,
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                 "Can't find requested entry point: %s", pszSymbolName);
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        return nullptr;
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    }
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    return (pSymbol);
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}
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#endif  // def _WIN32
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/* ==================================================================== */
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/*      Dummy implementation.                                           */
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/* ==================================================================== */
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#ifndef GOT_GETSYMBOL
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/************************************************************************/
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/*                            CPLGetSymbol()                            */
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/*                                                                      */
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/*      Dummy implementation.                                           */
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/************************************************************************/
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void *CPLGetSymbol(const char *pszLibrary, const char *pszEntryPoint)
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{
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    CPLDebug("CPL",
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             "CPLGetSymbol(%s,%s) called.  Failed as this is stub"
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             " implementation.",
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             pszLibrary, pszEntryPoint);
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    return nullptr;
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}
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#endif