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https://github.com/python/cpython
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![Thomas Heller](/assets/img/avatar_default.png)
table' of the dll, to make sure that the dll really was build for the correct Python version. It does this by looking for an entry 'pythonXY.dll' (X.Y is the Python version number). The code now checks the size of the dll's import table before reading entries from it. Before this patch, the code crashed trying to read the import table when the size was zero (as in Win2k's wmi.dll, for example). Look for imports of 'pythonXY_d.dll' in a debug build instead of 'pythonXY.dll'. Fixes SF 951851: Crash when reading "import table" of certain windows dlls. Already backported to the 2.3 branch.
256 lines
7.3 KiB
C
256 lines
7.3 KiB
C
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/* Support for dynamic loading of extension modules */
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#include <windows.h>
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#include <direct.h>
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#include <ctype.h>
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#include "Python.h"
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#include "importdl.h"
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const struct filedescr _PyImport_DynLoadFiletab[] = {
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#ifdef _DEBUG
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{"_d.pyd", "rb", C_EXTENSION},
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{"_d.dll", "rb", C_EXTENSION},
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#else
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{".pyd", "rb", C_EXTENSION},
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{".dll", "rb", C_EXTENSION},
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#endif
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{0, 0}
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};
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/* Case insensitive string compare, to avoid any dependencies on particular
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C RTL implementations */
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static int strcasecmp (char *string1, char *string2)
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{
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int first, second;
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do {
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first = tolower(*string1);
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second = tolower(*string2);
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string1++;
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string2++;
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} while (first && first == second);
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return (first - second);
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}
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/* Function to return the name of the "python" DLL that the supplied module
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directly imports. Looks through the list of imported modules and
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returns the first entry that starts with "python" (case sensitive) and
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is followed by nothing but numbers until the separator (period).
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Returns a pointer to the import name, or NULL if no matching name was
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located.
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This function parses through the PE header for the module as loaded in
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memory by the system loader. The PE header is accessed as documented by
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Microsoft in the MSDN PE and COFF specification (2/99), and handles
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both PE32 and PE32+. It only worries about the direct import table and
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not the delay load import table since it's unlikely an extension is
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going to be delay loading Python (after all, it's already loaded).
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If any magic values are not found (e.g., the PE header or optional
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header magic), then this function simply returns NULL. */
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#define DWORD_AT(mem) (*(DWORD *)(mem))
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#define WORD_AT(mem) (*(WORD *)(mem))
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static char *GetPythonImport (HINSTANCE hModule)
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{
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unsigned char *dllbase, *import_data, *import_name;
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DWORD pe_offset, opt_offset;
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WORD opt_magic;
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int num_dict_off, import_off;
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/* Safety check input */
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if (hModule == NULL) {
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return NULL;
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}
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/* Module instance is also the base load address. First portion of
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memory is the MS-DOS loader, which holds the offset to the PE
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header (from the load base) at 0x3C */
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dllbase = (unsigned char *)hModule;
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pe_offset = DWORD_AT(dllbase + 0x3C);
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/* The PE signature must be "PE\0\0" */
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if (memcmp(dllbase+pe_offset,"PE\0\0",4)) {
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return NULL;
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}
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/* Following the PE signature is the standard COFF header (20
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bytes) and then the optional header. The optional header starts
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with a magic value of 0x10B for PE32 or 0x20B for PE32+ (PE32+
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uses 64-bits for some fields). It might also be 0x107 for a ROM
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image, but we don't process that here.
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The optional header ends with a data dictionary that directly
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points to certain types of data, among them the import entries
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(in the second table entry). Based on the header type, we
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determine offsets for the data dictionary count and the entry
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within the dictionary pointing to the imports. */
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opt_offset = pe_offset + 4 + 20;
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opt_magic = WORD_AT(dllbase+opt_offset);
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if (opt_magic == 0x10B) {
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/* PE32 */
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num_dict_off = 92;
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import_off = 104;
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} else if (opt_magic == 0x20B) {
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/* PE32+ */
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num_dict_off = 108;
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import_off = 120;
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} else {
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/* Unsupported */
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return NULL;
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}
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/* Now if an import table exists, offset to it and walk the list of
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imports. The import table is an array (ending when an entry has
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empty values) of structures (20 bytes each), which contains (at
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offset 12) a relative address (to the module base) at which a
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string constant holding the import name is located. */
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if (DWORD_AT(dllbase + opt_offset + num_dict_off) >= 2) {
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/* We have at least 2 tables - the import table is the second
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one. But still it may be that the table size is zero */
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if (0 == DWORD_AT(dllbase + opt_offset + import_off + sizeof(DWORD)))
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return NULL;
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import_data = dllbase + DWORD_AT(dllbase +
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opt_offset +
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import_off);
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while (DWORD_AT(import_data)) {
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import_name = dllbase + DWORD_AT(import_data+12);
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if (strlen(import_name) >= 6 &&
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!strncmp(import_name,"python",6)) {
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char *pch;
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/* Ensure python prefix is followed only
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by numbers to the end of the basename */
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pch = import_name + 6;
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#ifdef _DEBUG
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while (*pch && pch[0] != '_' && pch[1] != 'd' && pch[2] != '.') {
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#else
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while (*pch && *pch != '.') {
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#endif
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if (*pch >= '0' && *pch <= '9') {
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pch++;
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} else {
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pch = NULL;
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break;
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}
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}
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if (pch) {
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/* Found it - return the name */
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return import_name;
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}
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}
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import_data += 20;
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}
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}
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return NULL;
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}
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dl_funcptr _PyImport_GetDynLoadFunc(const char *fqname, const char *shortname,
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const char *pathname, FILE *fp)
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{
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dl_funcptr p;
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char funcname[258], *import_python;
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PyOS_snprintf(funcname, sizeof(funcname), "init%.200s", shortname);
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{
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HINSTANCE hDLL = NULL;
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char pathbuf[260];
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LPTSTR dummy;
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/* We use LoadLibraryEx so Windows looks for dependent DLLs
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in directory of pathname first. However, Windows95
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can sometimes not work correctly unless the absolute
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path is used. If GetFullPathName() fails, the LoadLibrary
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will certainly fail too, so use its error code */
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if (GetFullPathName(pathname,
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sizeof(pathbuf),
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pathbuf,
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&dummy))
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/* XXX This call doesn't exist in Windows CE */
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hDLL = LoadLibraryEx(pathname, NULL,
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LOAD_WITH_ALTERED_SEARCH_PATH);
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if (hDLL==NULL){
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char errBuf[256];
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unsigned int errorCode;
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/* Get an error string from Win32 error code */
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char theInfo[256]; /* Pointer to error text
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from system */
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int theLength; /* Length of error text */
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errorCode = GetLastError();
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theLength = FormatMessage(
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FORMAT_MESSAGE_FROM_SYSTEM, /* flags */
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NULL, /* message source */
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errorCode, /* the message (error) ID */
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0, /* default language environment */
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(LPTSTR) theInfo, /* the buffer */
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sizeof(theInfo), /* the buffer size */
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NULL); /* no additional format args. */
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/* Problem: could not get the error message.
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This should not happen if called correctly. */
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if (theLength == 0) {
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PyOS_snprintf(errBuf, sizeof(errBuf),
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"DLL load failed with error code %d",
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errorCode);
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} else {
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size_t len;
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/* For some reason a \r\n
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is appended to the text */
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if (theLength >= 2 &&
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theInfo[theLength-2] == '\r' &&
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theInfo[theLength-1] == '\n') {
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theLength -= 2;
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theInfo[theLength] = '\0';
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}
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strcpy(errBuf, "DLL load failed: ");
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len = strlen(errBuf);
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strncpy(errBuf+len, theInfo,
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sizeof(errBuf)-len);
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errBuf[sizeof(errBuf)-1] = '\0';
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}
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PyErr_SetString(PyExc_ImportError, errBuf);
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return NULL;
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} else {
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char buffer[256];
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#ifdef _DEBUG
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PyOS_snprintf(buffer, sizeof(buffer), "python%d%d_d.dll",
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#else
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PyOS_snprintf(buffer, sizeof(buffer), "python%d%d.dll",
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#endif
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PY_MAJOR_VERSION,PY_MINOR_VERSION);
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import_python = GetPythonImport(hDLL);
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if (import_python &&
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strcasecmp(buffer,import_python)) {
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PyOS_snprintf(buffer, sizeof(buffer),
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"Module use of %.150s conflicts "
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"with this version of Python.",
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import_python);
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PyErr_SetString(PyExc_ImportError,buffer);
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FreeLibrary(hDLL);
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return NULL;
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}
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}
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p = GetProcAddress(hDLL, funcname);
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}
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return p;
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}
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