Question

everyone… I’ve just started to learn how to create process and thread using Windows API. My code does work if I want thread to display integer on the screen but it doesn’t work when using array of chars… Can someone tell me what am I doing wrong? The code:

#include<stdio.h>
#include<Windows.h>
#include<conio.h>
#include<tchar.h>
#include<strsafe.h>
#include<string.h>

#define N 4
#define bufferSize 255

DWORD WINAPI Threader(LPVOID Parameter);

typedef struct Data {
    char value[bufferSize];
} Data, *pToData;

int main()
{
    int i;
    char c[bufferSize];
    pToData threadData[N];
    HANDLE handleArray[N];
    DWORD threadID[N];

    FILE *file=fopen("niti.txt", "r");

    for(i=0; i<N; i++)
    {
        fscanf(file, "%s", c);
        threadData[i] = (pToData) HeapAlloc(GetProcessHeap(), HEAP_ZERO_MEMORY, sizeof(Data));
        strcpy(threadData[i]->value, c);
        handleArray[i]=CreateThread(NULL, 0, Threader, threadData[i], 0, &threadID[i]);
    }

    WaitForMultipleObjects(N, handleArray, TRUE, INFINITE);

    for(i=0; i<N; i++)
    {
        CloseHandle(handleArray[i]);
        if(threadData[i] != NULL)
        {
            HeapFree(GetProcessHeap(), 0, threadData[i]);
            threadData[i] = NULL;
        }
    }

    fclose(file);

    return 0;
}

DWORD WINAPI Threader(LPVOID Parameter)
{
    HANDLE hStdOut;
    TCHAR messageBuffer[bufferSize];
    size_t cchStringSize;
    DWORD dwChars;
    pToData dataArray;
    char temp[bufferSize];

    hStdOut = GetStdHandle(STD_OUTPUT_HANDLE);
    if( hStdOut == INVALID_HANDLE_VALUE )
        return 1;

    dataArray=(pToData)Parameter;

    StringCchPrintf(messageBuffer, bufferSize, TEXT("Parameter = %s\n"), dataArray->value); 
    StringCchLength(messageBuffer, bufferSize, &cchStringSize);
    WriteConsole(hStdOut, messageBuffer, (DWORD)cchStringSize, &dwChars, NULL);

    return 0;
}

If I change value in my struct to int and do the same in main the output is correct. Any suggestions?
Thank you!

Answer 1

You are probably compiling for Unicode but outputting a char array. Your symptoms sound like an encoding mismatch and Unicode output function mis-matched against ANSI char array is the mismatch that results in lots of questions marks.

In other words I hypothesise that your code resolves StringCchPrintf as StringCchPrintfW. And you then fail to satisfy the contract by passing char* rather than wchar_t* when you pass dataArray->value.

Use wchar_t or TCHAR instead of char for dataArray->value. Or call the A version of the output functions. Or compile for ANSI.