[PATCH] Strip \\?\ prefix from Perl path in win32/win32.c:set_w32_module_name()

[Jan Dubois]

Windows supports the \\?\ prefix to pass filenames longer than MAX_PATH
directly to the underlying file system functions without going through
the normal Win32 preprocessing (making file names absolute, turning
slashes into backslashes etc). Perl doesn't deal will these long
filenames as file/path buffers are allocated with MAX_PATH+1 bytes
almost everywhere. Besides, \\?\ should really only be used with Unicode
APIs anyways.

However, when Perl is started through a \\?\ prefixed path, e.g. with

start \\?\c:\perl\bin\perl -e"print qq($_\n) for @INC;<>"

then Win32 reports the module filename as \\?\c:\perl\bin\perl58.dll,
which in turn leads Perl to add //?/c:/perl/lib and //?/c:/perl/site/lib
to @INC which are now invalid names because you can't use forward slashes
with the \\?\ prefix.

The easiest way around this is to just strip the prefix from the module
filename. We'll immediately pass it to win32_longpath(), which only
supports MAX_PATH characters anyways.

Cheers,
-Jan

PS: In case you really want to know, I ran into this issue with a DLL
having a dependency on perl58.dll and being loaded by IIS. :)

--- win32/win32.c.~1~ Thu Jun 16 11:27:57 2005
+++ win32/win32.c Thu Jun 16 11:27:57 2005
@@ -138,6 +138,10 @@
: w32_perldll_handle),
w32_module_name, sizeof(w32_module_name));

+ /* remove \\?\ prefix */
+ if (memcmp(w32_module_name, "\\\\?\\", 4) == 0)
+ memmove(w32_module_name, w32_module_name+4, strlen(w32_module_name+4)+1);
+
/* try to get full path to binary (which may be mangled when perl is
* run from a 16-bit app) */
/*PerlIO_printf(Perl_debug_log, "Before %s\n", w32_module_name);*/
End of Patch.

[Steve Hay]

Jan Dubois wrote:

>The easiest way around this is to just strip the prefix from the module
>filename. We'll immediately pass it to win32_longpath(), which only
>supports MAX_PATH characters anyways.
>
>

Thanks, applied to bleadperl as #24880.

>Cheers,
>-Jan
>
>PS: In case you really want to know, I ran into this issue with a DLL
> having a dependency on perl58.dll and being loaded by IIS. :)
>
>--- win32/win32.c.~1~ Thu Jun 16 11:27:57 2005
>+++ win32/win32.c Thu Jun 16 11:27:57 2005
>@@ -138,6 +138,10 @@
> : w32_perldll_handle),
> w32_module_name, sizeof(w32_module_name));
>
>+ /* remove \\?\ prefix */
>+ if (memcmp(w32_module_name, "\\\\?\\", 4) == 0)
>+ memmove(w32_module_name, w32_module_name+4, strlen(w32_module_name+4)+1);
>+
> /* try to get full path to binary (which may be mangled when perl is
> * run from a 16-bit app) */
> /*PerlIO_printf(Perl_debug_log, "Before %s\n", w32_module_name);*/
>End of Patch.
>

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