Initial data commit

Task/Array-length/C/array-length-4.c

@@ -0,0 +1,112 @@
+#define _CRT_SECURE_NO_WARNINGS    // turn off panic warnings
+#define _CRT_NONSTDC_NO_WARNINGS   // enable old-gold POSIX names in MSVS
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+
+#define N 10
+
+// Fixed size global arrays
+
+static const int scGlobal[N];
+const int cGlobal[N];
+static int sGlobal[N];
+int Global[N];
+
+#define TEST(A, N)                                                             \
+ do {                                                                          \
+    puts("");                                                                  \
+    printf("directly called:          sizeof(%8s) = %2d,  length = %2d,  %s\n",\
+        #A,                                                                    \
+        sizeof(A),                                                             \
+        sizeof(A) / sizeof(int),                                               \
+        sizeof(A) / sizeof(int) == N ? "pass" : "fail");                       \
+                                                                               \
+    test1(#A, A, N);                                                           \
+    test2(#A, A, N);                                                           \
+    test3(#A, A, N);                                                           \
+} while (0);
+
+void test1(char* name, int* A, int n)
+{
+    printf("as parameter int* A:      sizeof(%8s) = %2d,  length = %2d,  %s\n",
+        name,
+        sizeof(A),
+        sizeof(A) / sizeof(int),
+        sizeof(A) / sizeof(int) == n ? "pass" : "fail");
+}
+
+void test2(char* name, int A[], int n)
+{
+    printf("as parameter int A[]:     sizeof(%8s) = %2d,  length = %2d,  %s\n",
+        name,
+        sizeof(A),
+        sizeof(A) / sizeof(int),
+        sizeof(A) / sizeof(int) == n ? "pass" : "fail");
+}
+
+void test3(char* name, int A[10], int n)
+{
+    printf("as parameter int A[10]:   sizeof(%8s) = %2d,  length = %2d,  %s\n",
+        name,
+        sizeof(A),
+        sizeof(A) / sizeof(int),
+        sizeof(A) / sizeof(int) == n ? "pass" : "fail");
+}
+
+
+int main(int argc, char argv[])
+{
+    // Fixed size local arrays (defined inside curly braces block)
+
+    static const int scLocal[N];
+    const int cLocal[N];
+    static int sLocal[N];
+    auto int aLocal[N];
+    int Local[N];
+
+    // Fixed size VLA arrays can/should be used instead dynamically alocated
+    // blocks. VLA has not implemented in Microsoft Visual Studio C.
+
+    srand(time(NULL));
+    int n = N + rand() % 2; // the value of n is unknow in the compile time?
+
+#ifndef _MSC_VER
+    int vlaLocal[n];
+#endif
+
+    // Memory blocks as ersatz arrays. This is not all possible ways to allocate
+    // memory. There are other functions, like LocalAlloc, HeapAlloc, sbreak...
+    // Don't use alloca in any serious program - this function is really bad
+    // choice - it can corrupt the program stack and generate a stack overflow.
+
+    int* mBlock = (int*)malloc(n * sizeof(int));
+    int* cBlock = (int*)calloc(n, sizeof(int));
+    int* aBlock = (int*)_alloca(n * sizeof(int)); // don't use in your programs!
+
+    TEST(scGlobal, N);
+    TEST(cGlobal, N);
+    TEST(sGlobal, N);
+    TEST(Global, N);
+
+    TEST(scLocal, N);
+    TEST(cLocal, N);
+    TEST(sLocal, N);
+    TEST(aLocal, N);
+    TEST(Local, N);
+
+#ifndef _MSC_VER
+    TEST(vlaLocal, n);
+#endif
+
+    TEST(mBlock, N);
+    TEST(cBlock, N);
+    TEST(aBlock, N);
+
+    free(mBlock, N);
+    free(cBlock, N);
+    // free must not be called on aBlock
+
+    return 0;
+}