builtin: fix -d debug_realloc, add realloc_data/3

vlib/builtin/array.v

@@ -86,7 +86,6 @@ fn new_array_from_c_array_no_alloc(len int, cap int, elm_size int, c_array voidp
 }
 
 // Private function. Doubles array capacity if needed.
-[inline]
 fn (mut a array) ensure_cap(required int) {
 	if required <= a.cap {
 		return
@@ -98,7 +97,7 @@ fn (mut a array) ensure_cap(required int) {
 	new_size := cap * a.element_size
 	mut new_data := byteptr(0)
 	if a.cap > 0 {
-		new_data = unsafe { v_realloc(a.data, new_size) }
+		new_data = unsafe { realloc_data(a.data, a.cap * a.element_size, new_size) }
 	} else {
 		new_data = vcalloc(new_size)
 	}

vlib/builtin/builtin.c.v

@@ -209,31 +209,55 @@ pub fn v_realloc(b byteptr, n int) byteptr {
 			C.memcpy(new_ptr, b, n)
 		}
 	} $else {
-		$if debug_realloc ? {
-			// NB: this is slower, but helps debugging memory problems.
-			// The main idea is to always force reallocating:
-			// 1) allocate a new memory block
-			// 2) copy the old to the new
-			// 3) fill the old with 0x57 (`W`)
-			// 4) free the old block
-			// => if there is still a pointer to the old block somewhere
-			//    it will point to memory that is now filled with 0x57.
-			unsafe {
-				new_ptr = malloc(n)
-				C.memcpy(new_ptr, b, n)
-				C.memset(b, 0x57, n)
-				C.free(b)
-			}
-		} $else {
-			new_ptr = unsafe { C.realloc(b, n) }
-			if new_ptr == 0 {
-				panic('realloc($n) failed')
-			}
+		new_ptr = unsafe { C.realloc(b, n) }
+		if new_ptr == 0 {
+			panic('realloc($n) failed')
 		}
 	}
 	return new_ptr
 }
 
+// realloc_data resizes the memory block pointed by `old_data` to `new_size`
+// bytes. `old_data` must be a pointer to an existing memory block, previously
+// allocated with `malloc`, `v_calloc` or `vcalloc`, of size `old_data`.
+// realloc_data returns a pointer to the new location of the block.
+// NB: if you know the old data size, it is preferable to call `realloc_data`,
+// instead of `v_realloc`, at least during development, because `realloc_data`
+// can make debugging easier, when you compile your program with
+// `-d debug_realloc`.
+[unsafe]
+pub fn realloc_data(old_data byteptr, old_size int, new_size int) byteptr {
+	$if prealloc {
+		unsafe {
+			new_ptr := malloc(new_size)
+			C.memcpy(new_ptr, old_data, old_size)
+			return new_ptr
+		}
+	}
+	$if debug_realloc ? {
+		// NB: this is slower, but helps debugging memory problems.
+		// The main idea is to always force reallocating:
+		// 1) allocate a new memory block
+		// 2) copy the old to the new
+		// 3) fill the old with 0x57 (`W`)
+		// 4) free the old block
+		// => if there is still a pointer to the old block somewhere
+		//    it will point to memory that is now filled with 0x57.
+		unsafe {
+			new_ptr := malloc(new_size)
+			C.memcpy(new_ptr, old_data, old_size)
+			C.memset(old_data, 0x57, old_size)
+			C.free(old_data)
+			return new_ptr
+		}
+	}
+	nptr := unsafe { C.realloc(old_data, new_size) }
+	if nptr == 0 {
+		panic('realloc_data($new_size) failed')
+	}
+	return nptr
+}
+
 // v_calloc dynamically allocates a zeroed `n` bytes block of memory on the heap.
 // v_calloc returns a `byteptr` pointing to the memory address of the allocated space.
 pub fn v_calloc(n int) byteptr {

vlib/builtin/map.v

@@ -142,12 +142,14 @@ fn (d &DenseArray) has_index(i int) bool {
 // The growth-factor is roughly 1.125 `(x + (x >> 3))`
 [inline]
 fn (mut d DenseArray) expand() int {
+	old_cap := d.cap
+	old_size := d.slot_bytes * old_cap
 	if d.cap == d.len {
 		d.cap += d.cap >> 3
 		unsafe {
-			d.data = v_realloc(d.data, d.slot_bytes * d.cap)
+			d.data = realloc_data(d.data, old_size, d.slot_bytes * d.cap)
 			if d.deletes != 0 {
-				d.all_deleted = v_realloc(d.all_deleted, d.cap)
+				d.all_deleted = realloc_data(d.all_deleted, old_cap, d.cap)
 				C.memset(d.all_deleted + d.len, 0, d.cap - d.len)
 			}
 		}
@@ -185,9 +187,10 @@ fn (mut d DenseArray) zeros_to_end() {
 		free(d.all_deleted)
 	}
 	d.len = count
+	old_cap := d.cap
 	d.cap = if count < 8 { 8 } else { count }
 	unsafe {
-		d.data = v_realloc(d.data, d.slot_bytes * d.cap)
+		d.data = realloc_data(d.data, d.slot_bytes * old_cap, d.slot_bytes * d.cap)
 	}
 }
 
@@ -406,10 +409,12 @@ fn (mut m map) meta_greater(_index u32, _metas u32, kvi u32) {
 [inline]
 fn (mut m map) ensure_extra_metas(probe_count u32) {
 	if (probe_count << 1) == m.extra_metas {
+		size_of_u32 := sizeof(u32)
+		old_mem_size := (m.even_index + 2 + m.extra_metas)
 		m.extra_metas += extra_metas_inc
 		mem_size := (m.even_index + 2 + m.extra_metas)
 		unsafe {
-			x := v_realloc(byteptr(m.metas), int(sizeof(u32) * mem_size))
+			x := realloc_data(byteptr(m.metas), int(size_of_u32 * old_mem_size), int(size_of_u32 * mem_size))
 			m.metas = &u32(x)
 			C.memset(m.metas + mem_size - extra_metas_inc, 0, int(sizeof(u32) * extra_metas_inc))
 		}
@@ -477,6 +482,7 @@ fn (mut m map) expand() {
 fn (mut m map) rehash() {
 	meta_bytes := sizeof(u32) * (m.even_index + 2 + m.extra_metas)
 	unsafe {
+		// TODO: use realloc_data here too
 		x := v_realloc(byteptr(m.metas), int(meta_bytes))
 		m.metas = &u32(x)
 		C.memset(m.metas, 0, meta_bytes)

vlib/os/os_c.v

@@ -445,6 +445,7 @@ pub fn get_raw_stdin() []byte {
 	$if windows {
 		unsafe {
 			block_bytes := 512
+			mut old_size := block_bytes
 			mut buf := malloc(block_bytes)
 			h_input := C.GetStdHandle(C.STD_INPUT_HANDLE)
 			mut bytes_read := 0
@@ -456,7 +457,9 @@ pub fn get_raw_stdin() []byte {
 				if !res {
 					break
 				}
-				buf = v_realloc(buf, offset + block_bytes + (block_bytes - bytes_read))
+				new_size := offset + block_bytes + (block_bytes - bytes_read)
+				buf = realloc_data(buf, old_size, new_size)
+				old_size = new_size
 			}
 			return array{
 				element_size: 1