[Please don't top post on this list.]
On 8/3/2019 5:02 PM, Denis Vnoukov wrote:
> Yes, gcvt is legacy. But there is no one Linux distribution which has no gcvt
> in
> the world.
> Moreover gcvt present into MSVC, Intel C, mingw, etc..
> It is true to have gcvt with right declaration.
> FD_ZERO(&read_fd); <== with -Wold-style-cast produced real bogus and
> suspicious
> warning which looks like bug
> GetTickCount64(); <== recommended part of WINAPI and must be avail via
> windows.h
> _BitScanReverse64 and _BitScanForward64 must be with "unsigned long *":
> unsigned char _BitScanForward64(
> unsigned long * Index,
> unsigned __int64 Mask
> );
> due to ms specification as well...
There are several mistakes (not GCC bugs) in your program.
1. As I already said in my first message, you need to define the appropriate
feature-test macro in order to get the declaration of gcvt. (I suggested
defining _XOPEN_SOURCE to 500, and that in fact works.)
2. The Microsoft documentation for GetTickCount64 says, "To compile an
application that uses this function, define _WIN32_WINNT as 0x0600 or later."
You didn't do this.
3. The Microsoft documentation for _BitScanForward64 says that the first
argument is of type 'unsigned long *'. You assumed that Microsoft's unsigned
long would be the same size as Cygwin's. You can avoid this problem by using
ULONG instead of unsigned long.
I'm attaching a fixed version of your program that compiles without warnings
and
runs without crashing on 64-bit Cygwin.
Ken
#define _XOPEN_SOURCE 500
#define _WIN32_WINNT 0x0600
#include <stdlib.h>
#include <stdio.h>
#include <sys/select.h>
#include <windows.h>
#include <stdint.h>
#include <intrin.h>
int
main()
{
char buf[50];
char * str = gcvt (3.141592653589793238462643383279502884197169399375, 49,
buf);
printf ("buffer: %s", str);
fd_set read_fd;
FD_ZERO (&read_fd);
GetTickCount64 ();
ULONG index;
uint64_t b = 0xbedabedadeadc0de;
_BitScanForward64 (&index, b);
_BitScanReverse64 (&index, b);
return 0;
}
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