Merge 10c4bf53ca into f845fa04a0

Closes #21815.

lib/std/debug/MemoryAccessor.zig

@@ -48,7 +48,8 @@ fn read(ma: *MemoryAccessor, address: usize, buf: []u8) bool {
                 switch (linux.E.init(bytes_read)) {
                     .SUCCESS => return bytes_read == buf.len,
                     .FAULT => return false,
-                    .INVAL, .PERM, .SRCH => unreachable, // own pid is always valid
+                    .INVAL, .SRCH => unreachable, // own pid is always valid
+                    .PERM => {}, // Known to happen in containers.
                     .NOMEM => {},
                     .NOSYS => {}, // QEMU is known not to implement this syscall.
                     else => unreachable, // unexpected

lib/std/math/complex.zig

@@ -115,6 +115,11 @@ pub fn Complex(comptime T: type) type {
         pub fn magnitude(self: Self) T {
             return @sqrt(self.re * self.re + self.im * self.im);
         }
+
+        /// Returns the squared magnitude of a complex number.
+        pub fn sqrmag(self: Self) T {
+            return self.re * self.re + self.im * self.im;
+        }
     };
 }
 
@@ -189,6 +194,13 @@ test "magnitude" {
     try testing.expect(math.approxEqAbs(f32, c, 5.83095, epsilon));
 }
 
+test "sqrmag" {
+    const a = Complex(f32).init(5, 3);
+    const c = a.sqrmag();
+
+    try testing.expect(math.approxEqAbs(f32, c, math.pow(f32, a.magnitude(), 2), epsilon));
+}
+
 test {
     _ = @import("complex/abs.zig");
     _ = @import("complex/acosh.zig");