Memory Leak?

[nmoagit]

Disclaimer: I don't know what I am doing. I am trying to learn Zig and I noticed this and I was wondering if you could help explain what is going on.

EDIT: I can stop the leak by freeing the allocation inside of the loop. Is this the correct thing to do?

Zig: zig-linux-x86_64-0.14.0-dev

trying chameleon, /magurotuna/zig-deque, std.io.getStdOut

// setup: 
var gpa = std.heap.GeneralPurposeAllocator(.{}){};
defer _ = gpa.deinit();
const allocator = gpa.allocator();

var deque = try Deque(usize).init(allocator);
defer deque.deinit();
   
try deque.pushBack(1);
try deque.pushBack(2);
try deque.pushFront(42);

const writer = std.io.getStdOut().writer();
var c = Chameleon.initRuntime(.{ .allocator = allocator });
   
var it = deque.iterator();

then when trying to print values using the iterator

// NO MEMORY LEAK
 while (it.next()) |val| {
    try writer.print("{d} \n", .{val.*});
}

^-- No memory leak

// MEMORY LEAK
 while (it.next()) |val| {
    try writer.print("{s} \n", .{try c.green().bold().fmt("{d}", .{val.*})});
}

^-- memory leak

// FIXED? MEMORY LEAK
 while (it.next()) |val| {
    const fmt_text = try c.green().bold().fmt("{d}", .{val.*});
    try writer.print("{s} \n", .{});
    defer allocator.free(fmt_text);
}

^-- FIXED? memory leak. Is this correct?

and this is the leak message:

error(gpa): memory address 0x7f1f4ab20000 leaked:
/zig/zig-linux-x86_64-0.14.0-dev.3286+05d8b565a/lib/std/mem.zig:3317:36: 0x1043d50 in concatMaybeSentinel__anon_3572 (deque_test)
    const buf = try allocator.alloc(T, total_len);
                                   ^
/zig/zig-linux-x86_64-0.14.0-dev.3286+05d8b565a/lib/std/mem.zig:3291:31: 0x103d588 in concat__anon_2508 (deque_test)
    return concatMaybeSentinel(allocator, T, slices, null);
                              ^
/.cache/zig/p/12208314a762057bf5ed82b26b02cbfcf426066b9920bfdd1ddcb68d1d0c55c45ce3/src/api/Runtime.zig:25:30: 0x103d1a2 in fmt__anon_2476 (deque_test)
        return std.mem.concat(self.allocator, u8, &.{ self.open.items, formatted, self.close.items });
                             ^
../src/main.zig:34:62: 0x103dc48 in main (deque_test)
        try writer.print("{s} \n", .{try c.green().bold().fmt("{d}", .{val.*})});
                                                             ^
/zig/zig-linux-x86_64-0.14.0-dev.3286+05d8b565a/lib/std/start.zig:656:37: 0x103ceda in posixCallMainAndExit (deque_test)
            const result = root.main() catch |err| {
                                    ^
/zig/zig-linux-x86_64-0.14.0-dev.3286+05d8b565a/lib/std/start.zig:271:5: 0x103ca8d in _start (deque_test)
    asm volatile (switch (native_arch) {
    ^

error(gpa): memory address 0x7f1f4ab20020 leaked:
/zig/zig-linux-x86_64-0.14.0-dev.3286+05d8b565a/lib/std/mem.zig:3317:36: 0x1043d50 in concatMaybeSentinel__anon_3572 (deque_test)
    const buf = try allocator.alloc(T, total_len);
                                   ^
/zig/zig-linux-x86_64-0.14.0-dev.3286+05d8b565a/lib/std/mem.zig:3291:31: 0x103d588 in concat__anon_2508 (deque_test)
    return concatMaybeSentinel(allocator, T, slices, null);
                              ^
/.cache/zig/p/12208314a762057bf5ed82b26b02cbfcf426066b9920bfdd1ddcb68d1d0c55c45ce3/src/api/Runtime.zig:25:30: 0x103d1a2 in fmt__anon_2476 (deque_test)
        return std.mem.concat(self.allocator, u8, &.{ self.open.items, formatted, self.close.items });
                             ^
../src/main.zig:34:62: 0x103dc48 in main (deque_test)
        try writer.print("{s} \n", .{try c.green().bold().fmt("{d}", .{val.*})});
                                                             ^
/zig/zig-linux-x86_64-0.14.0-dev.3286+05d8b565a/lib/std/start.zig:656:37: 0x103ceda in posixCallMainAndExit (deque_test)
            const result = root.main() catch |err| {
                                    ^
/zig/zig-linux-x86_64-0.14.0-dev.3286+05d8b565a/lib/std/start.zig:271:5: 0x103ca8d in _start (deque_test)
    asm volatile (switch (native_arch) {
    ^

error(gpa): memory address 0x7f1f4ab20040 leaked:
/zig/zig-linux-x86_64-0.14.0-dev.3286+05d8b565a/lib/std/mem.zig:3317:36: 0x1043d50 in concatMaybeSentinel__anon_3572 (deque_test)
    const buf = try allocator.alloc(T, total_len);
                                   ^
/zig/zig-linux-x86_64-0.14.0-dev.3286+05d8b565a/lib/std/mem.zig:3291:31: 0x103d588 in concat__anon_2508 (deque_test)
    return concatMaybeSentinel(allocator, T, slices, null);
                              ^
/.cache/zig/p/12208314a762057bf5ed82b26b02cbfcf426066b9920bfdd1ddcb68d1d0c55c45ce3/src/api/Runtime.zig:25:30: 0x103d1a2 in fmt__anon_2476 (deque_test)
        return std.mem.concat(self.allocator, u8, &.{ self.open.items, formatted, self.close.items });
                             ^
../src/main.zig:34:62: 0x103dc48 in main (deque_test)
        try writer.print("{s} \n", .{try c.green().bold().fmt("{d}", .{val.*})});
                                                             ^
/zig/zig-linux-x86_64-0.14.0-dev.3286+05d8b565a/lib/std/start.zig:656:37: 0x103ceda in posixCallMainAndExit (deque_test)
            const result = root.main() catch |err| {
                                    ^
/zig/zig-linux-x86_64-0.14.0-dev.3286+05d8b565a/lib/std/start.zig:271:5: 0x103ca8d in _start (deque_test)
    asm volatile (switch (native_arch) {
    ^

[tr1ckydev]

I see you haven't called c.deinit() anywhere in the above code which is the reason it leaks the memory. Report back if it does resolve the issue!

[evaneliasyoung]

@nmoagit, I believe that the fix you mentioned is the correct solution here.