Account for realloc moving the memory in gebs_arena_realloc()

example/arena.c

@@ -8,7 +8,7 @@ typedef struct {
 
 int main(void)
 {
-    Gebs_Arena *arena = gebs_arena_make(1024);
+    Gebs_Arena *arena = gebs_arena_make(sizeof(int));
     defer { gebs_arena_destroy(arena); }
 
     Ints ints = {0};

gebs.c

@@ -9,11 +9,11 @@ int main(int argc, char ** argv)
         gebs_mkdir("build");
     }
 
-    if (gebs_needs_rebuild_many("build/self_rebuild", "example/self_rebuild.c")) {
+    if (gebs_needs_rebuild_many("build/self_rebuild", "example/self_rebuild.c", "gebs.h")) {
         if (GEBS_CMD("gcc", "-ggdb", "-o", "build/self_rebuild", "example/self_rebuild.c") != 0)
             return 1;
     }
-    if (gebs_needs_rebuild_many("build/arena", "example/arena.c")) {
+    if (gebs_needs_rebuild_many("build/arena", "example/arena.c", "gebs.h")) {
         if (GEBS_CMD("gcc", "-ggdb", "-o", "build/arena", "example/arena.c") != 0)
             return 1;
     }

gebs.h

@@ -23,6 +23,7 @@
 #include <stdio.h>
 #include <stddef.h>
 #include <stdlib.h>
+#include <inttypes.h>
 
 #if GEBS_PLATFORM == GEBS_PLATFORM_POSIX
 #   include <unistd.h>
@@ -33,6 +34,8 @@
 #   error "Unknown GEBS_PLATFORM"
 #endif
 
+#define discard __attribute__((unused))
+
 // ----------------------------------------------------------------------------
 // Defer macro
 // ----------------------------------------------------------------------------
@@ -239,9 +242,12 @@ void gebs_rebuild_self1_alloc(Gebs_Allocator *alloc, int argc, char ** argv,
 #define gebs_needs_rebuild_many(out, ...) \
 ({ \
     const char *__deps[] = { __VA_ARGS__ }; \
-    bool __ok = true; \
+    bool __ok = false; \
     for (size_t __i = 0; __i < sizeof(__deps)/sizeof(__deps[0]); __i++) { \
-        __ok = __ok && gebs_needs_rebuild((out), __deps[__i]); \
+        if (gebs_needs_rebuild((out), __deps[__i])) { \
+            __ok = true; \
+            break; \
+        } \
     } \
     __ok; \
 })
@@ -327,22 +333,19 @@ Gebs_Allocator gebs_default_allocator = {
     .realloc = &gebs_default_allocator_realloc,
 };
 
-void *gebs_default_allocator_malloc(void *self, size_t size)
+void *gebs_default_allocator_malloc(discard void *self, size_t size)
 {
-    (void)self;
     return malloc(size);
 }
 
-void gebs_default_allocator_free(void *self, void *memory)
+void gebs_default_allocator_free(discard void *self, void *memory)
 {
-    (void)self;
     free(memory);
 }
 
-void *gebs_default_allocator_realloc(void *self, void *memory,
-                                     size_t prev_size, size_t new_size)
+void *gebs_default_allocator_realloc(discard void *self, void *memory,
+                                     discard size_t prev_size, size_t new_size)
 {
-    (void)self;
     void *p = realloc(memory, new_size);
     return p;
 }
@@ -411,18 +414,18 @@ void *gebs_arena_malloc(void *self, size_t size)
     return a->region + (a->index - size);
 }
 
-void gebs_arena_free(void *self, void *memory)
+void gebs_arena_free(discard void *self, discard void *memory)
 {
-    (void)self;
-    (void)memory;
 }
 
-void *gebs_arena_realloc(void *self, void *memory, size_t prev_size, size_t new_size)
+void *gebs_arena_realloc(void *self, void *memory,
+                         discard size_t prev_size, size_t new_size)
 {
-    (void)prev_size;
-    (void)memory;
-    gebs_arena_expand((Gebs_Arena *)self, new_size);
-    return memory;
+    Gebs_Arena *a = (Gebs_Arena *)self;
+
+    uintptr_t offset = (char *)memory - a->region;
+    gebs_arena_expand(a, a->size + new_size);
+    return a->region + offset;
 }
 
 void gebs_arena_reset(Gebs_Arena *a)