Merge pull request #5797 from xackus/intcast-runtime-safety

stage1: `@intcast` runtime safety for unsigned -> signed of same bit count

5 files changed, 19 insertions, 7 deletions

diff --git a/lib/std/special/compiler_rt/clzsi2_test.zig b/lib/std/special/compiler_rt/clzsi2_test.zig
index ff94455846..8a2896fcb6 100644
--- a/lib/std/special/compiler_rt/clzsi2_test.zig
+++ b/lib/std/special/compiler_rt/clzsi2_test.zig
@@ -4,7 +4,7 @@ const testing = @import("std").testing;
 fn test__clzsi2(a: u32, expected: i32) void {
     var nakedClzsi2 = clzsi2.__clzsi2;
     var actualClzsi2 = @ptrCast(fn (a: i32) callconv(.C) i32, nakedClzsi2);
-    var x = @intCast(i32, a);
+    var x = @bitCast(i32, a);
     var result = actualClzsi2(x);
     testing.expectEqual(expected, result);
 }
diff --git a/lib/std/special/compiler_rt/int.zig b/lib/std/special/compiler_rt/int.zig
index eb731ee898..a72c13e233 100644
--- a/lib/std/special/compiler_rt/int.zig
+++ b/lib/std/special/compiler_rt/int.zig
@@ -244,7 +244,7 @@ pub fn __udivsi3(n: u32, d: u32) callconv(.C) u32 {
         //      r.all -= d.all;
         //      carry = 1;
         // }
-        const s = @intCast(i32, d -% r -% 1) >> @intCast(u5, n_uword_bits - 1);
+        const s = @bitCast(i32, d -% r -% 1) >> @intCast(u5, n_uword_bits - 1);
         carry = @intCast(u32, s & 1);
         r -= d & @bitCast(u32, s);
     }
diff --git a/lib/std/special/compiler_rt/udivmod.zig b/lib/std/special/compiler_rt/udivmod.zig
index 7d519c34cb..ba53d1dee0 100644
--- a/lib/std/special/compiler_rt/udivmod.zig
+++ b/lib/std/special/compiler_rt/udivmod.zig
@@ -184,7 +184,7 @@ pub fn udivmod(comptime DoubleInt: type, a: DoubleInt, b: DoubleInt, maybe_rem:
         //      carry = 1;
         // }
         r_all = @ptrCast(*align(@alignOf(SingleInt)) DoubleInt, &r[0]).*; // TODO issue #421
-        const s: SignedDoubleInt = @intCast(SignedDoubleInt, b -% r_all -% 1) >> (DoubleInt.bit_count - 1);
+        const s: SignedDoubleInt = @bitCast(SignedDoubleInt, b -% r_all -% 1) >> (DoubleInt.bit_count - 1);
         carry = @intCast(u32, s & 1);
         r_all -= b & @bitCast(DoubleInt, s);
         r = @ptrCast(*[2]SingleInt, &r_all).*; // TODO issue #421
diff --git a/src/codegen.cpp b/src/codegen.cpp
index 18ef7d9182..2f72861bc2 100644
--- a/src/codegen.cpp
+++ b/src/codegen.cpp
@@ -1535,9 +1535,11 @@ static LLVMValueRef gen_widen_or_shorten(CodeGen *g, bool want_runtime_safety, Z
         zig_unreachable();
     }
 
-    if (actual_type->id == ZigTypeIdInt &&
-        !wanted_type->data.integral.is_signed && actual_type->data.integral.is_signed &&
-        want_runtime_safety)
+    if (actual_type->id == ZigTypeIdInt && want_runtime_safety && (
+        // negative to unsigned
+        (!wanted_type->data.integral.is_signed && actual_type->data.integral.is_signed) ||
+        // unsigned would become negative
+        (wanted_type->data.integral.is_signed && !actual_type->data.integral.is_signed && actual_bits == wanted_bits)))
     {
         LLVMValueRef zero = LLVMConstNull(get_llvm_type(g, actual_type));
         LLVMValueRef ok_bit = LLVMBuildICmp(g->builder, LLVMIntSGE, expr_val, zero, "");
@@ -1547,7 +1549,7 @@ static LLVMValueRef gen_widen_or_shorten(CodeGen *g, bool want_runtime_safety, Z
         LLVMBuildCondBr(g->builder, ok_bit, ok_block, fail_block);
 
         LLVMPositionBuilderAtEnd(g->builder, fail_block);
-        gen_safety_crash(g, PanicMsgIdCastNegativeToUnsigned);
+        gen_safety_crash(g, actual_type->data.integral.is_signed ? PanicMsgIdCastNegativeToUnsigned : PanicMsgIdCastTruncatedData);
 
         LLVMPositionBuilderAtEnd(g->builder, ok_block);
     }
diff --git a/test/runtime_safety.zig b/test/runtime_safety.zig
index e60d115a00..e27ae7e16e 100644
--- a/test/runtime_safety.zig
+++ b/test/runtime_safety.zig
@@ -757,6 +757,16 @@ pub fn addCases(cases: *tests.CompareOutputContext) void {
         \\}
     );
 
+    cases.addRuntimeSafety("unsigned integer not fitting in cast to signed integer - same bit count",
+        \\pub fn panic(message: []const u8, stack_trace: ?*@import("builtin").StackTrace) noreturn {
+        \\    @import("std").os.exit(126);
+        \\}
+        \\pub fn main() void {
+        \\    var value: u8 = 245;
+        \\    var casted = @intCast(i8, value);
+        \\}
+    );
+
     cases.addRuntimeSafety("unwrap error",
         \\pub fn panic(message: []const u8, stack_trace: ?*@import("builtin").StackTrace) noreturn {
         \\    if (@import("std").mem.eql(u8, message, "attempt to unwrap error: Whatever")) {