From 69dd10144fc723d8006f2e563fc3edd82ee4b368 Mon Sep 17 00:00:00 2001
From: Jacob Young <jacobly@ziglang.org>
Date: Fri, 17 Jul 2026 11:33:42 -0400
Subject: [PATCH] Type: make `f80` not extern compatible on targets lacking
 such a type

Closes #35802
---
 src/Sema.zig | 2 +-
 src/Type.zig | 5 ++++-
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/Sema.zig b/src/Sema.zig
index 129b9104d385499e8443b4fc45dcf6c2e26497e8..bb2cd4eff32547c659ec0e7f14fddf3cc4b07d18 100644
--- a/src/Sema.zig
+++ b/src/Sema.zig
@@ -25675,7 +25675,6 @@ pub fn explainWhyTypeIsNotExtern(
 
         .@"opaque",
         .bool,
-        .float,
         .@"anyframe",
         => unreachable, // these *are* allowed
 
@@ -25684,6 +25683,7 @@ pub fn explainWhyTypeIsNotExtern(
             try sema.errNote(src_loc, msg, "SPIR-V runtime arrays must be the last field of an extern struct", .{});
         },
 
+        .float => try sema.errNote(src_loc, msg, "'{f}' is not extern compatible on this target", .{ty.fmt(pt)}),
         .pointer => if (ty.isSlice(zcu)) {
             try sema.errNote(src_loc, msg, "slices have no guaranteed in-memory representation", .{});
         } else {
diff --git a/src/Type.zig b/src/Type.zig
index 32e49a05c26a8ee5459164c02f987c92704f0f65..56b2388710b2b919a2a429fd3afa0dfa515bcf66 100644
--- a/src/Type.zig
+++ b/src/Type.zig
@@ -3122,7 +3122,6 @@ pub fn validateExtern(ty: Type, position: ExternPosition, zcu: *const Zcu) bool
 
         .@"opaque",
         .bool,
-        .float,
         .@"anyframe",
         => true,
 
@@ -3144,6 +3143,10 @@ pub fn validateExtern(ty: Type, position: ExternPosition, zcu: *const Zcu) bool
             24, 48 => zcu.getTarget().cpu.arch == .ez80,
             else => false,
         },
+        .float => switch (ty.floatBits(zcu.getTarget())) {
+            else => true,
+            80 => zcu.getTarget().cTypeBitSize(.longdouble) == 80,
+        },
         .@"fn" => {
             if (position != .other) return false;
             return validateExternCallconv(ty.fnCallingConvention(zcu));
-- 
2.54.0