Recursive function causing stack overflow

Question

I have a bit of code that is working except it is causing a stack overflow. I know the issue is caused because of recursion but I am not sure what I can do to stop it in this scenario.

The Code:

void FindFilesRecursively(LPCTSTR lpFolder) {
    TCHAR szFullPattern[MAX_PATH];
    WIN32_FIND_DATA FindFileData;
    HANDLE hFindFile;

    PathCombine(szFullPattern, lpFolder, (L"*"));
    hFindFile = FindFirstFile(szFullPattern, &FindFileData);
    if (wcscmp(FindFileData.cFileName, L".") == 0){
        FindNextFile(hFindFile, &FindFileData);
        if (wcscmp(FindFileData.cFileName, L"..") == 0) {
            FindNextFile(hFindFile, &FindFileData);
        }
    }
    if (hFindFile != INVALID_HANDLE_VALUE) {
        do {
            if (FindFileData.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY) {
                // found a subdirectory; recurse into it
                PathCombine(szFullPattern, lpFolder, FindFileData.cFileName);
                printf("FOLDER: %S\n", szFullPattern);
                FindFilesRecursively(szFullPattern);
            }
            printf("FILE: %S\n", FindFileData.cFileName);
        } while (FindNextFile(hFindFile, &FindFileData));
        FindClose(hFindFile);
    }
    printf("END\n");
}

Basically all it does it takes a folder/file path as argument and then it will print the name if it is a folder, or it will go recursively through the path and print everything. My debugger is hitting stack overflow at about 53 calls to this function. I am not sure where/how I should terminate a call to this function so that it doesn't cause the stack overflow.

Fyi, the checks fro '.' and '..' and an subsequent ignoring of said-same should be part of the loop; not assumed to optionally be the first (or first two) entries. As soon as the latter assumption fails, the entire loop will recurse indefinitely. — WhozCraig
– WhozCraig, Commented Aug 9, 2021 at 16:44
Take action on the value of hFindFile immediately: you are executing code based on the supposed data in FindFileData in between. — Weather Vane
– Weather Vane, Commented Aug 9, 2021 at 16:47
"If the function fails, the return value is zero and the contents of lpFindFileData are indeterminate." I suggest you have a single loop, which ignores "." and "..". — Weather Vane
– Weather Vane, Commented Aug 9, 2021 at 17:03

Flanker · Accepted Answer · 2021-08-09 18:39:52Z

When your code hits empty directory, it will backtrack to parent directory:

if (wcscmp(FindFileData.cFileName, L"..") == 0) {
        FindNextFile(hFindFile, &FindFileData);
    }
}
if (hFindFile != INVALID_HANDLE_VALUE) {

FindNextFile returns zero if no more entries, but your code doesn't check for it. Since hFindFile is not INVALID_HANDLE_VALUE, your code happily processes cached ".." as next found entry, but it will redirect to parent folder (and eventually produce SO). Here is the fixed code:

    void FindFilesRecursively(LPCTSTR lpFolder) {
    TCHAR szFullPattern[MAX_PATH];
    WIN32_FIND_DATA FindFileData;
    HANDLE hFindFile;

    PathCombine(szFullPattern, lpFolder, (L"*"));
    hFindFile = FindFirstFile(szFullPattern, &FindFileData);
    if (hFindFile != INVALID_HANDLE_VALUE) {
        do {
            if ((FindFileData.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY) != 0 && 
                wcscmp(FindFileData.cFileName, L".") != 0 && 
                wcscmp(FindFileData.cFileName, L"..") != 0) {
                // found a subdirectory, and it's neither .. nor ..; recurse into it
                PathCombine(szFullPattern, lpFolder, FindFileData.cFileName);
                printf("FOLDER: %S\n", szFullPattern);
                FindFilesRecursively(szFullPattern);
            }
            printf("FILE: %S\n", FindFileData.cFileName);
        } while (FindNextFile(hFindFile, &FindFileData));
        FindClose(hFindFile);
    }
    printf("END\n");
}

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