Question about having msvcrt*.dll and cygwin1.dll in one process
Jing Zhao
jing.zhao@ni.com
Mon Nov 17 08:47:00 GMT 2014
Hi all,
Cygwin FAQ 6.15 says that I cannot link with both MSVCRT*.dll and
cygwin1.dll since they are mutually exclusive. However, I can successfully
run a simple Windows console application which dynamically loads a dll
(compiled in Cygwin, thus linking to cygwin1.dll). The Windows console
application is built with Multi-threaded DLL (/MD). So what's the problem
of linking to both MSVCRT*.dll and cygwin1.dll. Am I missing anything?
// test.cpp, DLL code compiled in Cygwin
#include <stdio.h>
int hello(void)
{
printf ("welcome to linux world\n");
return 7777777;
}
This is the code to produce dll
$ gcc -g -O2 -c test.cpp
$ gcc -shared -o test.dll test.o
// main application compiled in MSVC, with /MD
#include <stdio.h>
#include <Windows.h>
int main()
{
char padding[32768];
memset(padding, 0, sizeof(padding));
HMODULE h = LoadLibrary(TEXT("C:\\cygwin64\\bin\\cygwin1.dll"));
if (!h)
{
DWORD code = GetLastError();
printf ("can't load cygwin1.dll, code %d\n", code);
return 0;
}
typedef void (WINAPI *INITFUC)();
INITFUC init = NULL;
init = (INITFUC) GetProcAddress(h, "cygwin_dll_init");
if (!init)
{
printf ("can't find cygwin_dll_init()\n");
return 0;
}
init();
h = LoadLibrary(TEXT("E:\\opensource\\Cygwin\\test\\test.dll"));
if (!h)
{
DWORD code = GetLastError();
printf ("can't load test.dll, code %d\n", code);
return 0;
}
typedef int (*MYFUNC)(void);
MYFUNC f = NULL;
f = (MYFUNC) GetProcAddress(h, "_Z5hellov");
if (!f)
{
printf ("can't find hello()\n");
return 0;
}
int res = (*f)();
printf ("res: %d\n", res);
printf ("it's over\n");
getchar();
return 0;
}
The outputs:
welcome to linux world
res: 7777777
it's over
So everything look fine. According to the FAQ 6.15, is there anything
that's potentially dangerous that I should be aware of, when linking both
msvcrt.dll and cygwin1.dll? Thanks a lot!
Thanks,
Jing Zhao @ Shanghai
Ext. 3273
8+ 7023273
--
Problem reports: http://cygwin.com/problems.html
FAQ: http://cygwin.com/faq/
Documentation: http://cygwin.com/docs.html
Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple
More information about the Cygwin
mailing list