Fixing C warnings (algorithm-archivists#934)

* Added warnings as errors for C/C++ code and fixed C warnings.

SConstruct

@@ -23,7 +23,7 @@ env = Environment(ENV=os.environ,
                             'Go': go_builder},
                   tools=['gcc', 'gnulink', 'g++', 'gas', 'gfortran'])
 
-env['CCFLAGS'] = ''
+env['CCFLAGS'] = '-Wall -Wextra -Werror'
 env['CXXFLAGS'] = '-std=c++17'
 env['ASFLAGS'] = '--64'
 

contents/IFS/code/c/IFS.c

@@ -20,7 +20,7 @@ void chaos_game(struct point *in, size_t in_n, struct point *out,
 
     struct point cur_point = {drand(), drand()};
 
-    for (int i = 0; i < out_n; ++i) {
+    for (size_t i = 0; i < out_n; ++i) {
         out[i] = cur_point;
         struct point tmp = random_element(in, in_n);
         cur_point.x = 0.5 * (cur_point.x + tmp.x);

contents/barnsley/code/c/barnsley.c

@@ -44,6 +44,7 @@ struct matrix select_array(struct matrix *hutchinson_op, double *probabilities,
         }
         rnd -= probabilities[i];
     }
+    return hutchinson_op[0];
 }
 
 // This is a general function to simulate a chaos game

contents/cooley_tukey/code/c/fft.c

@@ -6,7 +6,7 @@
 #include <time.h>
 #include <fftw3.h>
 
-void fft(double complex *x, int n) {
+void fft(double complex *x, size_t n) {
     double complex y[n];
     memset(y, 0, sizeof(y));
     fftw_plan p;
@@ -56,8 +56,8 @@ void cooley_tukey(double complex *X, const size_t N) {
 }
 
 void bit_reverse(double complex *X, size_t N) {
-    for (int i = 0; i < N; ++i) {
-        int n = i;
+    for (size_t i = 0; i < N; ++i) {
+        size_t n = i;
         int a = i;
         int count = (int)log2((double)N) - 1;
 
@@ -81,7 +81,7 @@ void iterative_cooley_tukey(double complex *X, size_t N) {
     bit_reverse(X, N);
 
     for (int i = 1; i <= log2((double)N); ++i) {
-        int stride = pow(2, i);
+        size_t stride = pow(2, i);
         double complex w = cexp(-2.0 * I * M_PI / stride);
         for (size_t j = 0; j < N; j += stride) {
             double complex v = 1.0;

contents/euclidean_algorithm/code/c/euclidean_example.c

@@ -1,40 +1,40 @@
 #include <stdio.h>
-#include <math.h>
+#include <stdlib.h>
 
 int euclid_mod(int a, int b) {
-    a = abs(a);
-    b = abs(b);
+  a = abs(a);
+  b = abs(b);
 
-    while (b != 0) {
-        int temp = b;
-        b = a % b;
-        a = temp;
-    }
+  while (b != 0) {
+    int temp = b;
+    b = a % b;
+    a = temp;
+  }
 
-    return a;
+  return a;
 }
 
 int euclid_sub(int a, int b) {
-    a = abs(a);
-    b = abs(b);
-
-    while (a != b) {
-        if (a > b) {
-            a -= b;
-        } else {
-            b -= a;
-        }
+  a = abs(a);
+  b = abs(b);
+
+  while (a != b) {
+    if (a > b) {
+      a -= b;
+    } else {
+      b -= a;
     }
+  }
 
-    return a;
+  return a;
 }
 
 int main() {
-    int check1 = euclid_mod(64 * 67, 64 * 81);
-    int check2 = euclid_sub(128 * 12, 128 * 77);
+  int check1 = euclid_mod(64 * 67, 64 * 81);
+  int check2 = euclid_sub(128 * 12, 128 * 77);
 
-    printf("%d\n", check1);
-    printf("%d\n", check2);
+  printf("%d\n", check1);
+  printf("%d\n", check2);
 
-    return 0;
+  return 0;
 }

contents/flood_fill/code/c/flood_fill.c

@@ -25,7 +25,7 @@ int inbounds(struct point p, struct canvas c) {
     return (p.x < 0 || p.y < 0 || p.y >= c.max_y || p.x >= c.max_x) ? 0 : 1;
 }
 
-int find_neighbors(struct canvas c, struct point p, int old_val, int new_val,
+int find_neighbors(struct canvas c, struct point p, int old_val, 
         struct point *neighbors) {
     int cnt = 0;
     struct point points[4] = {
@@ -90,7 +90,7 @@ void stack_fill(struct canvas c, struct point p, int old_val, int new_val) {
             c.data[cur_loc.x + c.max_x * cur_loc.y] = new_val;
 
             struct point neighbors[4];
-            int cnt = find_neighbors(c, cur_loc, old_val, new_val, neighbors);
+            int cnt = find_neighbors(c, cur_loc, old_val, neighbors);
 
             for (int i = 0; i < cnt; ++i) {
                 stack_push(&stk, neighbors[i]);
@@ -160,7 +160,7 @@ void queue_fill(struct canvas c, struct point p, int old_val, int new_val) {
             c.data[cur_loc.x + c.max_x * cur_loc.y] = new_val;
 
             struct point neighbors[4];
-            int cnt = find_neighbors(c, cur_loc, old_val, new_val, neighbors);
+            int cnt = find_neighbors(c, cur_loc, old_val, neighbors);
 
             for (int i = 0; i < cnt; ++i) {
                 enqueue(&q, neighbors[i]);
@@ -181,7 +181,7 @@ void recursive_fill(struct canvas c, struct point p, int old_val,
     c.data[p.x + c.max_x * p.y] = new_val;
 
     struct point neighbors[4];
-    int cnt = find_neighbors(c, p, old_val, new_val, neighbors);
+    int cnt = find_neighbors(c, p, old_val, neighbors);
 
     for (int i = 0; i < cnt; ++i) {
         recursive_fill(c, neighbors[i], old_val, new_val);

contents/gaussian_elimination/code/c/gaussian_elimination.c

@@ -47,31 +47,31 @@ void gaussian_elimination(double *a, const size_t rows, const size_t cols) {
     }
 }
 
-void back_substitution(const double *a, double *x, const size_t rows,
-                       const size_t cols) {
+void back_substitution(const double *a, double *x, const int rows,
+                       const int cols) {
 
     for (int i = rows - 1; i >= 0; --i) {
         double sum = 0.0;
 
-        for (size_t j = cols - 2; j > i; --j) {
+        for (int j = cols - 2; j > i; --j) {
             sum += x[j] * a[i * cols + j];
         }
 
         x[i] = (a[i * cols + cols - 1] - sum) / a[i * cols + i];
     }
 }
 
-void gauss_jordan(double *a, const size_t rows, const size_t cols) {
-    int row = 0;
+void gauss_jordan(double *a, const size_t cols) {
+    size_t row = 0;
 
-    for (int col = 0; col < cols - 1; ++col) {
+    for (size_t col = 0; col < cols - 1; ++col) {
         if (a[row * cols + col] != 0) {
-            for (int i = cols - 1; i > col - 1; --i) {
+            for (size_t i = cols - 1; i > col - 1; --i) {
                 a[row * cols + i] /= a[row * cols + col];
             }
 
-            for (int i = 0; i < row; ++i) {
-                for (int j = cols - 1; j > col - 1; --j) {
+            for (size_t i = 0; i < row; ++i) {
+                for (size_t j = cols - 1; j > col - 1; --j) {
                     a[i * cols + j] -= a[i * cols + col] * a[row * cols + j];
                 }
             }
@@ -99,7 +99,7 @@ int main() {
 
     printf("\nGauss-Jordan:\n");
 
-    gauss_jordan((double *)a, 3, 4);
+    gauss_jordan((double *)a, 4);
 
     for (size_t i = 0; i < 3; ++i) {
         printf("[");

contents/huffman_encoding/code/c/huffman.c

@@ -125,7 +125,7 @@ struct tree* generate_tree(const char* str) {
     }
 
     struct heap heap = { 0 };
-    for (int i = 0; i < sizeof(counts) / sizeof(int); ++i) {
+    for (size_t i = 0; i < sizeof(counts) / sizeof(int); ++i) {
         if (counts[i]) {
             struct tree* tree = calloc(1, sizeof(struct tree));
             tree->value = (char)i;
@@ -211,8 +211,6 @@ char* encode(const char* input, struct tree** huffman_tree,
     *codebook = generate_codebook(*huffman_tree);
 
     char* result = duplicate(get_code(codebook, *input));
-    int result_length = strlen(result);
-    int result_capacity = result_length;
 
     input += 1;
 

contents/split-operator_method/code/c/split_op.c

@@ -28,7 +28,7 @@ struct operators {
     double complex *wfc;
 };
 
-void fft(double complex *x, int n, bool inverse) {
+void fft(double complex *x, size_t n, bool inverse) {
     double complex y[n];
     memset(y, 0, sizeof(y));
     fftw_plan p;
@@ -139,8 +139,8 @@ void split_op(struct params par, struct operators opr) {
         sprintf(filename, "output%lu.dat", i);
         FILE *fp = fopen(filename, "w");
 
-        for (int i = 0; i < opr.size; ++i) {
-            fprintf(fp, "%d\t%f\t%f\n", i, density[i], creal(opr.v[i]));
+        for (size_t i = 0; i < opr.size; ++i) {
+            fprintf(fp, "%ld\t%f\t%f\n", i, density[i], creal(opr.v[i]));
         }
 
         fclose(fp);

contents/stable_marriage_problem/code/c/stable_marriage.c

@@ -20,11 +20,11 @@ void shuffle(size_t *array, size_t size) {
     }
 }
 
-void create_group(struct person *group, size_t size, bool are_men) {
+void create_group(struct person *group, size_t size) {
     for (size_t i = 0; i < size; ++i) {
         group[i].id = i;
         group[i].partner = NULL;
-        group[i].prefers = (size_t*)malloc(sizeof(size_t) * size);
+        group[i].prefers = malloc(sizeof(size_t) * size);
         group[i].index = 0;
 
         for (size_t j = 0; j < size; ++j) {
@@ -43,6 +43,7 @@ bool prefers_partner(size_t *prefers, size_t partner, size_t id, size_t size) {
             return false;
         }
     }
+    return true;
 }
 
 void stable_marriage(struct person *men, struct person *women, size_t size) {
@@ -85,8 +86,8 @@ int main() {
 
     struct person men[5], women[5];
 
-    create_group(men, 5, true);
-    create_group(women, 5, false);
+    create_group(men, 5);
+    create_group(women, 5);
 
     for (size_t i = 0; i < 5; ++i) {
         printf("preferences of man %zu: ", i);