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/******************************************************************************
*
* Project: Common Portability Library
* Purpose: Fetch a function pointer from a shared library / DLL.
* Author: Frank Warmerdam, warmerdam@pobox.com
*
******************************************************************************
* Copyright (c) 1999, Frank Warmerdam
* Copyright (c) 2009-2013, Even Rouault <even dot rouault at spatialys.com>
*
* SPDX-License-Identifier: MIT
****************************************************************************/
#include "cpl_port.h"
#include "cpl_conv.h"
#include <cstddef>
#include "cpl_config.h"
#include "cpl_error.h"
#include "cpl_string.h"
/* ==================================================================== */
/* Unix Implementation */
/* ==================================================================== */
/* MinGW32 might define HAVE_DLFCN_H, so skip the unix implementation */
#if defined(HAVE_DLFCN_H) && !defined(_WIN32)
#define GOT_GETSYMBOL
#include <dlfcn.h>
/************************************************************************/
/* CPLGetSymbol() */
/************************************************************************/
/**
* Fetch a function pointer from a shared library / DLL.
*
* This function is meant to abstract access to shared libraries and
* DLLs and performs functions similar to dlopen()/dlsym() on Unix and
* LoadLibrary() / GetProcAddress() on Windows.
*
* If no support for loading entry points from a shared library is available
* this function will always return NULL. Rules on when this function
* issues a CPLError() or not are not currently well defined, and will have
* to be resolved in the future.
*
* Currently CPLGetSymbol() doesn't try to:
* <ul>
* <li> prevent the reference count on the library from going up
* for every request, or given any opportunity to unload
* the library.
* <li> Attempt to look for the library in non-standard
* locations.
* <li> Attempt to try variations on the symbol name, like
* pre-pending or post-pending an underscore.
* </ul>
*
* Some of these issues may be worked on in the future.
*
* @param pszLibrary the name of the shared library or DLL containing
* the function. May contain path to file. If not system supplies search
* paths will be used.
* @param pszSymbolName the name of the function to fetch a pointer to.
* @return A pointer to the function if found, or NULL if the function isn't
* found, or the shared library can't be loaded.
*/
void *CPLGetSymbol(const char *pszLibrary, const char *pszSymbolName)
{
void *pLibrary = dlopen(pszLibrary, RTLD_LAZY);
if (pLibrary == nullptr)
{
CPLError(CE_Failure, CPLE_AppDefined, "%s", dlerror());
return nullptr;
}
void *pSymbol = dlsym(pLibrary, pszSymbolName);
#if (defined(__APPLE__) && defined(__MACH__))
/* On mach-o systems, C symbols have a leading underscore and depending
* on how dlcompat is configured it may or may not add the leading
* underscore. If dlsym() fails, add an underscore and try again.
*/
if (pSymbol == nullptr)
{
char withUnder[256] = {};
snprintf(withUnder, sizeof(withUnder), "_%s", pszSymbolName);
pSymbol = dlsym(pLibrary, withUnder);
}
#endif
if (pSymbol == nullptr)
{
CPLError(CE_Failure, CPLE_AppDefined, "%s", dlerror());
// Do not call dlclose here. misc.py:misc_6() demonstrates the crash.
// coverity[leaked_storage]
return nullptr;
}
// coverity[leaked_storage] It is not safe to call dlclose.
return (pSymbol);
}
#endif /* def __unix__ && defined(HAVE_DLFCN_H) */
/* ==================================================================== */
/* Windows Implementation */
/* ==================================================================== */
#if defined(_WIN32)
#define GOT_GETSYMBOL
#include <windows.h>
/************************************************************************/
/* CPLGetSymbol() */
/************************************************************************/
void *CPLGetSymbol(const char *pszLibrary, const char *pszSymbolName)
{
void *pLibrary = nullptr;
void *pSymbol = nullptr;
// Avoid error boxes to pop up (#5211, #5525).
UINT uOldErrorMode =
SetErrorMode(SEM_NOOPENFILEERRORBOX | SEM_FAILCRITICALERRORS);
#if defined(_MSC_VER) || __MSVCRT_VERSION__ >= 0x0601
if (CPLTestBool(CPLGetConfigOption("GDAL_FILENAME_IS_UTF8", "YES")))
{
wchar_t *pwszFilename =
CPLRecodeToWChar(pszLibrary, CPL_ENC_UTF8, CPL_ENC_UCS2);
pLibrary = LoadLibraryW(pwszFilename);
CPLFree(pwszFilename);
}
else
#endif
{
pLibrary = LoadLibraryA(pszLibrary);
}
if (pLibrary <= (void *)HINSTANCE_ERROR)
{
LPVOID lpMsgBuf = nullptr;
int nLastError = GetLastError();
// Restore old error mode.
SetErrorMode(uOldErrorMode);
FormatMessage(
FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM |
FORMAT_MESSAGE_IGNORE_INSERTS,
nullptr, nLastError, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
reinterpret_cast<LPTSTR>(&lpMsgBuf), 0, nullptr);
CPLError(CE_Failure, CPLE_AppDefined,
"Can't load requested DLL: %s\n%d: %s", pszLibrary, nLastError,
static_cast<const char *>(lpMsgBuf));
return nullptr;
}
// Restore old error mode.
SetErrorMode(uOldErrorMode);
pSymbol = reinterpret_cast<void *>(
GetProcAddress(static_cast<HINSTANCE>(pLibrary), pszSymbolName));
if (pSymbol == nullptr)
{
CPLError(CE_Failure, CPLE_AppDefined,
"Can't find requested entry point: %s", pszSymbolName);
return nullptr;
}
return (pSymbol);
}
#endif // def _WIN32
/* ==================================================================== */
/* Dummy implementation. */
/* ==================================================================== */
#ifndef GOT_GETSYMBOL
/************************************************************************/
/* CPLGetSymbol() */
/* */
/* Dummy implementation. */
/************************************************************************/
void *CPLGetSymbol(const char *pszLibrary, const char *pszEntryPoint)
{
CPLDebug("CPL",
"CPLGetSymbol(%s,%s) called. Failed as this is stub"
" implementation.",
pszLibrary, pszEntryPoint);
return nullptr;
}
#endif
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