C language > Beginner questions

Converting 32 bit code to 64 bit code

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John Z:
Here is a nice summary about things to consider and do to convert 32 bit into 64 bit code.
It is from Oracle, June 2016 - yes I know I'm way behind  :) :) :)

John Z

Vortex:
Hi John,

Thanks. Here is another link :

http://www.codeproject.com/Articles/17263/Moving-to-Windows-Vista-x64

John Z:
When upgrading another program to 64 bit I ran into this -
strlen() in 32 bit returns size_t which seems to be DWORD
strlen() in 64 bit returns size_t which seems to be unsigned long long int

so far so good - however in fileapi.h the WriteFile function
WINBASEAPI BOOL WINAPI WriteFile(HANDLE, LPCVOID, DWORD, LPDWORD, LPOVERLAPPED);
doesn't change parm 3 so when compiling for 64 bits you get
Log_To_File.c(101): warning #2215: Conversion from 'unsigned long long int' to 'unsigned long int'; possible loss of data or unexpected result.

The only way I can see is either suppress the #2215 warning or cast (DWORD)strlen()

Doesn't seem to be a WriteFile64 .... and WriteFile is not marked as depreciated..

Thoughts?

John Z

So far upgrading from my old 32 bit programs to 64 bit has been relatively simple.  Benefit is questionable other than future proofing against 32 bit support disappearing.

WiiLF23:
"If your application needs to handle large files and you want to work with 64-bit sizes, you might consider using the WriteFileEx function, which has a different signature that includes a LARGE_INTEGER parameter for the file offset. This function is designed to work with large files on 64-bit systems."


--- Code: ---WINBASEAPI BOOL WINAPI WriteFileEx(
    HANDLE hFile,
    LPCVOID lpBuffer,
    DWORD nNumberOfBytesToWrite,
    LPOVERLAPPED lpOverlapped,
    LPOVERLAPPED_COMPLETION_ROUTINE lpCompletionRoutine
);

--- End code ---

John Z:
Thanks WiiLF23,

Appreciate the input - I did look at that and it seems overly complex for the simple log file entry.

There are other file methods of course, and it is just a warning, but to me it points out that 64 bit seems to not be fully implemented across the winbaseapi by Microsoft.

John Z

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