Task: File extension is in extensions list

C: 

#define _CRT_SECURE_NO_WARNINGS

#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <locale.h>
#include <string.h>

#ifdef _Bool
#include <stdbool.h>
#else
#define bool int
#define true  1
#define false 0
#endif


int checkFileExtension(char* fileName, char* fileExtensions)
{
    char* fileExtension = fileExtensions;

    if ( *fileName )
    {
        while ( *fileExtension )
        {
            int fileNameLength = strlen(fileName);
            int extensionLength = strlen(fileExtension);
            if ( fileNameLength >= extensionLength )
            {
                char* a = fileName + fileNameLength - extensionLength;
                char* b = fileExtension;
                while ( *a && toupper(*a++) == toupper(*b++) )
                    ;
                if ( !*a )
                    return true;
            }
            fileExtension += extensionLength + 1;
        }
    }
    return false;
}

void printExtensions(char* extensions)
{
    while( *extensions )
    {
        printf("%s\n", extensions);
        extensions += strlen(extensions) + 1;
    }
}

bool test(char* fileName, char* extension, bool expectedResult)
{
    bool result = checkFileExtension(fileName,extension);
    bool returnValue = result == expectedResult;
    printf("%20s  result: %-5s  expected: %-5s  test %s\n", 
        fileName,
        result         ? "true"   : "false",
        expectedResult ? "true"   : "false", 
        returnValue    ? "passed" : "failed" );
    return returnValue;
}

int main(void)
{
    static char extensions[] = ".zip\0.rar\0.7z\0.gz\0.archive\0.A##\0.tar.bz2\0";

    setlocale(LC_ALL,"");

    printExtensions(extensions);
    printf("\n");

    if ( test("MyData.a##",         extensions,true )
    &&   test("MyData.tar.Gz",      extensions,true )
    &&   test("MyData.gzip",        extensions,false)
    &&   test("MyData.7z.backup",   extensions,false)
    &&   test("MyData...",          extensions,false)
    &&   test("MyData",             extensions,false)
    &&   test("MyData_v1.0.tar.bz2",extensions,true )
    &&   test("MyData_v1.0.bz2",    extensions,false) 
    &&   test("filename",           extensions,false)
    )
        printf("\n%s\n", "All tests passed.");
    else
        printf("\n%s\n", "Last test failed.");

    printf("\n%s\n", "press enter");
    getchar();
    return 0;
}


C++: #include <algorithm>
#include <cctype>
#include <iomanip>
#include <iostream>
#include <string>
#include <vector>

bool endsWithIgnoreCase(const std::string& str, const std::string& suffix) {
    const size_t n1 = str.length();
    const size_t n2 = suffix.length();
    if (n1 < n2)
        return false;
    return std::equal(str.begin() + (n1 - n2), str.end(), suffix.begin(),
        [](char c1, char c2) {
            return std::tolower(static_cast<unsigned char>(c1))
                == std::tolower(static_cast<unsigned char>(c2));
    });
}

bool filenameHasExtension(const std::string& filename,
                          const std::vector<std::string>& extensions) {
    return std::any_of(extensions.begin(), extensions.end(),
        [&filename](const std::string& extension) {
            return endsWithIgnoreCase(filename, "." + extension);
    });
}

void test(const std::string& filename,
          const std::vector<std::string>& extensions) {
    std::cout << std::setw(20) << std::left << filename
        << ": " << std::boolalpha
        << filenameHasExtension(filename, extensions) << '\n';
}

int main() {
    const std::vector<std::string> extensions{"zip", "rar", "7z",
        "gz", "archive", "A##", "tar.bz2"};
    test("MyData.a##", extensions);
    test("MyData.tar.Gz", extensions);
    test("MyData.gzip", extensions);
    test("MyData.7z.backup", extensions);
    test("MyData...", extensions);
    test("MyData", extensions);
    test("MyData_v1.0.tar.bz2", extensions);
    test("MyData_v1.0.bz2", extensions);
    return 0;
}