Add helper function concat_strings_alloc() to tools module

src/boxes.c

@@ -157,22 +157,11 @@ static int can_read_dir(const char *dirname)
 static char *combine(const char *dirname, const char *filename)
 {
     const size_t dirname_len = strlen(dirname);
-    const size_t filename_len = strlen(filename);
 
-    char *result = (char *) malloc(dirname_len + filename_len + 2);
-    char *p = result;
-
-    strcpy(result, dirname);   // TODO leverage concat_strings
-    p += dirname_len;
-    if (dirname[dirname_len - 1] != '/') {
-        result[dirname_len] = '/';
-        p++;
+    if (dirname[dirname_len - 1] == '/') {
+        return concat_strings_alloc(2, dirname, filename);
     }
-    strcpy(p, filename);
-    p += filename_len;
-    *p = '\0';
-
-    return result;
+    return concat_strings_alloc(3, dirname, "/", filename);
 }
 
 
@@ -223,10 +212,7 @@ static char *from_env_var(const char *env_var, const char *postfix)
         fprintf(stderr, "%s: from_env_var(): getenv(\"%s\") --> %s\n", PROJECT, env_var, result);
     #endif
     if (result != NULL) {
-        size_t result_len = strlen(result) + strlen(postfix) + 1;
-        char *combined = (char *) malloc(result_len);
-        concat_strings(combined, result_len, 2, result, postfix);
-        result = combined;
+        result = concat_strings_alloc(2, result, postfix);
     }
     return result;
 }
@@ -374,7 +360,7 @@ static int open_yy_config_file(const char *config_file_name)
         fprintf(stderr, "%s: Couldn't open config file '%s' for input\n", PROJECT, config_file_name);
         return 1;
     }
-    yyfilename = config_file_name;
+    yyfilename = (char *) config_file_name;
     yyin = new_yyin;
     return 0;
 }

src/tools.c

@@ -213,6 +213,44 @@ void concat_strings(char *dst, int max_len, int count, ...)
 
 
 
+char *concat_strings_alloc(size_t count, ...)
+{
+    if (count < 1) {
+        return strdup("");
+    }
+
+    size_t total_len = 0;
+    const char *src;
+    va_list va;
+
+    va_start (va, count);
+    for (size_t i = 0; i < count; i++) {
+        src = va_arg (va, const char *);
+        if (src != NULL) {
+            total_len += strlen(src);
+        }
+    }
+    va_end (va);
+
+    char *result = malloc(total_len + 1);
+    char *p = result;
+
+    va_start (va, count);
+    for (size_t i = 0; i < count; i++) {
+        src = va_arg (va, const char *);
+        if (src != NULL && src[0] != '\0') {
+            strcpy(p, src);
+            p += strlen(src);
+        }
+    }
+    va_end (va);
+
+    *p = '\0';
+    return result;
+}
+
+
+
 int empty_line(const line_t *line)
 /*
  *  Return true if line is empty.

src/tools.h

@@ -30,6 +30,7 @@
 #include "boxes.h"
 
 
+
 #define BMAX(a, b) ({                    /* return the larger value */ \
     __typeof__ (a) _a = (a); \
     __typeof__ (b) _b = (b); \
@@ -64,6 +65,15 @@ int strisyes(const char *s);
 
 int strisno(const char *s);
 
+/**
+ * Concatenate variable number of strings into one. This would normally be achieved via snprintf(), but that's not
+ * available on all platforms where boxes is compiled.
+ * @param <count> number of strings given in the following
+ * @param <...> the strings
+ * @returns a new string, for which new memory was allocated
+ */
+char *concat_strings_alloc(size_t count, ...);
+
 void concat_strings(char *dst, int max_len, int count, ...);
 
 char *tabbify_indent(const size_t lineno, char *indentspc, const size_t indentspc_len);