all: various fixes for [heap]/auto-heap handling (#10033)

vlib/builtin/linux_bare/libc_impl.v

@@ -9,7 +9,7 @@ pub fn memcpy(dest &C.void, src &C.void, n size_t) &C.void {
 			dest_[i] = src_[i]
 		}
 	}
-	return dest
+	return unsafe { dest }
 }
 
 [export: 'malloc']
@@ -37,7 +37,7 @@ fn realloc(old_area &C.void, new_size size_t) &C.void {
 	}
 	old_size := unsafe { *(&u64(old_area - sizeof(u64))) }
 	if u64(new_size) <= old_size {
-		return old_area
+		return unsafe { old_area }
 	} else {
 		new_area := unsafe { malloc(int(new_size)) }
 		unsafe { memmove(new_area, old_area, size_t(old_size)) }
@@ -54,7 +54,7 @@ fn memset(s &C.void, c int, n size_t) &C.void {
 			s_[i] = char(c)
 		}
 	}
-	return s
+	return unsafe { s }
 }
 
 [unsafe]
@@ -74,7 +74,7 @@ fn memmove(dest &C.void, src &C.void, n size_t) &C.void {
 		}
 	}
 	unsafe { free(temp_buf) }
-	return dest
+	return unsafe { dest }
 }
 
 [export: 'calloc']

vlib/builtin/string.v

@@ -77,7 +77,7 @@ pub fn tos(s &byte, len int) string {
 		panic('tos(): nil string')
 	}
 	return string{
-		str: s
+		str: unsafe { s }
 		len: len
 	}
 }
@@ -96,7 +96,7 @@ pub fn tos2(s &byte) string {
 		panic('tos2: nil string')
 	}
 	return string{
-		str: s
+		str: unsafe { s }
 		len: unsafe { vstrlen(s) }
 	}
 }
@@ -146,7 +146,7 @@ pub fn tos_lit(s &char) string {
 [unsafe]
 pub fn (bp &byte) vstring() string {
 	return string{
-		str: bp
+		str: unsafe { bp }
 		len: unsafe { C.strlen(&char(bp)) }
 	}
 }
@@ -156,7 +156,7 @@ pub fn (bp &byte) vstring() string {
 [unsafe]
 pub fn (bp &byte) vstring_with_len(len int) string {
 	return string{
-		str: bp
+		str: unsafe { bp }
 		len: len
 		is_lit: 0
 	}
@@ -194,7 +194,7 @@ pub fn (cp &char) vstring_with_len(len int) string {
 [unsafe]
 pub fn (bp &byte) vstring_literal() string {
 	return string{
-		str: bp
+		str: unsafe { bp }
 		len: unsafe { C.strlen(&char(bp)) }
 		is_lit: 1
 	}
@@ -205,7 +205,7 @@ pub fn (bp &byte) vstring_literal() string {
 [unsafe]
 pub fn (bp &byte) vstring_literal_with_len(len int) string {
 	return string{
-		str: bp
+		str: unsafe { bp }
 		len: len
 		is_lit: 1
 	}