Make alloc interface replaceable

- Add `x` prefix to malloc, calloc, realloc, and free
  (eg: malloc -> xmalloc)
- By default, they are replaced with stdlib's functions at build
- You can use custom functions by defining `PRISM_CUSTOM_ALLOCATOR` macro

Author: hasumikin

docs/build_system.md

@@ -82,6 +82,16 @@ For instance, you can build a static library `libprism.a` targeting the Arm Cort
 
 The build process internally looks up `_POSIX_MAPPED_FILES` and `_WIN32` macros to determine whether the functions of the memory map are available on the target platform.
 
+### Building prism with custom memory allocator
+
+If you need to use memory allocation functions implemented outside of the standard library, follow these steps:
+
+* Add `-D PRISM_CUSTOM_ALLOCATOR` to the build options
+* Additionally, include `-I [path/to/custom_allocator]` where your `custom_allocator.h` is located
+* Link the implementation of `custom_allocator.c` that contains functions declared in `custom_allocator.h`
+
+For further clarity, refer to `include/prism/defines.h`.
+
 ### Building prism from source as a C library
 
 All of the source files match `src/**/*.c` and all of the headers match `include/**/*.h`.

ext/prism/extension.c

@@ -310,15 +310,15 @@ dump(int argc, VALUE *argv, VALUE self) {
 
 #ifdef PRISM_DEBUG_MODE_BUILD
     size_t length = pm_string_length(&input);
-    char* dup = malloc(length);
+    char* dup = xmalloc(length);
     memcpy(dup, pm_string_source(&input), length);
     pm_string_constant_init(&input, dup, length);
 #endif
 
     VALUE value = dump_input(&input, &options);
 
 #ifdef PRISM_DEBUG_MODE_BUILD
-    free(dup);
+    xfree(dup);
 #endif
 
     pm_string_free(&input);
@@ -733,15 +733,15 @@ parse(int argc, VALUE *argv, VALUE self) {
 
 #ifdef PRISM_DEBUG_MODE_BUILD
     size_t length = pm_string_length(&input);
-    char* dup = malloc(length);
+    char* dup = xmalloc(length);
     memcpy(dup, pm_string_source(&input), length);
     pm_string_constant_init(&input, dup, length);
 #endif
 
     VALUE value = parse_input(&input, &options);
 
 #ifdef PRISM_DEBUG_MODE_BUILD
-    free(dup);
+    xfree(dup);
 #endif
 
     pm_string_free(&input);

include/prism/defines.h

@@ -125,4 +125,27 @@
 #   define isinf(x) (sizeof(x) == sizeof(float) ? !_finitef(x) : !_finite(x))
 #endif
 
+/**
+ * If you build prism with a custom allocator, configure it with "-D PRISM_CUSTOM_ALLOCATOR"
+ * to use your own allocator that defines xmalloc, xrealloc, xcalloc, and xfree.
+ * For example, your `custom_allocator.h` file could look like this:
+ * ```
+ * #ifndef PRISM_CUSTOM_ALLOCATOR_H
+ * #define PRISM_CUSTOM_ALLOCATOR_H
+ * #define xmalloc      my_malloc
+ * #define xrealloc     my_realloc
+ * #define xcalloc      my_calloc
+ * #define xfree        my_free
+ * #endif
+ * ```
+ */
+#ifdef PRISM_CUSTOM_ALLOCATOR
+#   include "custom_allocator.h"
+#else
+#   define xmalloc      malloc
+#   define xrealloc     realloc
+#   define xcalloc      calloc
+#   define xfree        free
+#endif
+
 #endif

include/prism/util/pm_list.h

@@ -33,7 +33,7 @@
  * } pm_int_node_t;
  *
  * pm_list_t list = { 0 };
- * pm_int_node_t *node = malloc(sizeof(pm_int_node_t));
+ * pm_int_node_t *node = xmalloc(sizeof(pm_int_node_t));
  * node->value = 5;
  *
  * pm_list_append(&list, &node->node);

src/diagnostic.c

@@ -336,7 +336,7 @@ pm_diagnostic_level(pm_diagnostic_id_t diag_id) {
  */
 bool
 pm_diagnostic_list_append(pm_list_t *list, const uint8_t *start, const uint8_t *end, pm_diagnostic_id_t diag_id) {
-    pm_diagnostic_t *diagnostic = (pm_diagnostic_t *) calloc(sizeof(pm_diagnostic_t), 1);
+    pm_diagnostic_t *diagnostic = (pm_diagnostic_t *) xcalloc(sizeof(pm_diagnostic_t), 1);
     if (diagnostic == NULL) return false;
 
     *diagnostic = (pm_diagnostic_t) {
@@ -367,15 +367,15 @@ pm_diagnostic_list_append_format(pm_list_t *list, const uint8_t *start, const ui
         return false;
     }
 
-    pm_diagnostic_t *diagnostic = (pm_diagnostic_t *) calloc(sizeof(pm_diagnostic_t), 1);
+    pm_diagnostic_t *diagnostic = (pm_diagnostic_t *) xcalloc(sizeof(pm_diagnostic_t), 1);
     if (diagnostic == NULL) {
         return false;
     }
 
     size_t length = (size_t) (result + 1);
-    char *message = (char *) malloc(length);
+    char *message = (char *) xmalloc(length);
     if (message == NULL) {
-        free(diagnostic);
+        xfree(diagnostic);
         return false;
     }
 
@@ -404,8 +404,8 @@ pm_diagnostic_list_free(pm_list_t *list) {
     while (node != NULL) {
         pm_diagnostic_t *next = (pm_diagnostic_t *) node->node.next;
 
-        if (node->owned) free((void *) node->message);
-        free(node);
+        if (node->owned) xfree((void *) node->message);
+        xfree(node);
 
         node = next;
     }

src/options.c

@@ -86,7 +86,7 @@ pm_options_version_set(pm_options_t *options, const char *version, size_t length
 PRISM_EXPORTED_FUNCTION bool
 pm_options_scopes_init(pm_options_t *options, size_t scopes_count) {
     options->scopes_count = scopes_count;
-    options->scopes = calloc(scopes_count, sizeof(pm_options_scope_t));
+    options->scopes = xcalloc(scopes_count, sizeof(pm_options_scope_t));
     return options->scopes != NULL;
 }
 
@@ -105,7 +105,7 @@ pm_options_scope_get(const pm_options_t *options, size_t index) {
 PRISM_EXPORTED_FUNCTION bool
 pm_options_scope_init(pm_options_scope_t *scope, size_t locals_count) {
     scope->locals_count = locals_count;
-    scope->locals = calloc(locals_count, sizeof(pm_string_t));
+    scope->locals = xcalloc(locals_count, sizeof(pm_string_t));
     return scope->locals != NULL;
 }
 
@@ -132,10 +132,10 @@ pm_options_free(pm_options_t *options) {
             pm_string_free(&scope->locals[local_index]);
         }
 
-        free(scope->locals);
+        xfree(scope->locals);
     }
 
-    free(options->scopes);
+    xfree(options->scopes);
 }
 
 /**