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returned-stack-reference

Nursery

What This Rule Does​

Checks for functions that return references to stack-allocated memory.

warning

This rule is still in early development. PRs to improve it are welcome.

It is illegal to use stack-allocated memory outside of the function that allocated it. Once that function returns and the stack is popped, the memory is no longer valid and may cause segfaults or undefined behavior.

const std = @import("std");
fn foo() *u32 {
  var x: u32 = 1; // x is on the stack
  return &x;
}
fn bar() void {
  const x = foo();
  std.debug.print("{d}\n", .{x}); // crashes
}

Examples​

Examples of incorrect code for this rule:

const std = @import("std");
fn foo() *u32 {
  var x: u32 = 1;
  return &x;
}
fn bar() []u32 {
  var x: [1]u32 = .{1};
  return x[0..];
}

Examples of correct code for this rule:

fn foo() *u32 {
  var x = std.heap.page_allocator.create(u32);
  x.* = 1;
  return x;
}

Configuration​

This rule has no configuration.