[embedded] Allow string-interpolating fatalError in Embedded Swift

stdlib/public/core/Assert.swift

@@ -275,16 +275,26 @@ public func preconditionFailure(
 ///   - line: The line number to print along with `message`. The default is the
 ///     line number where `fatalError(_:file:line:)` is called.
 @_transparent
-@_unavailableInEmbedded
 #if $Embedded
 @_disfavoredOverload
 #endif
 public func fatalError(
   _ message: @autoclosure () -> String = String(),
   file: StaticString = #file, line: UInt = #line
 ) -> Never {
+#if !$Embedded
   _assertionFailure("Fatal error", message(), file: file, line: line,
     flags: _fatalErrorFlags())
+#else
+  if _isDebugAssertConfiguration() {
+    _assertionFailure("Fatal error", message(), file: file, line: line,
+      flags: _fatalErrorFlags())
+  } else {
+    Builtin.condfail_message(true._value,
+      StaticString("fatal error").unsafeRawPointer)
+    Builtin.unreachable()
+  }
+#endif
 }
 
 #if $Embedded

stdlib/public/core/AssertCommon.swift

@@ -134,15 +134,16 @@ internal func _assertionFailure(
 #if !$Embedded
 @inline(never)
 #else
+@_disfavoredOverload
 @inline(__always)
 #endif
 @_semantics("programtermination_point")
-@_unavailableInEmbedded
 internal func _assertionFailure(
   _ prefix: StaticString, _ message: String,
   file: StaticString, line: UInt,
   flags: UInt32
 ) -> Never {
+#if !$Embedded
   prefix.withUTF8Buffer {
     (prefix) -> Void in
     var message = message
@@ -158,6 +159,14 @@ internal func _assertionFailure(
       }
     }
   }
+#else
+  if _isDebugAssertConfiguration() {
+    var message = message
+    message.withUTF8 { (messageUTF8) -> Void in
+      _embeddedReportFatalErrorInFile(prefix: prefix, message: messageUTF8, file: file, line: line)
+    }
+  }
+#endif
 
   Builtin.int_trap()
 }

stdlib/public/core/EmbeddedPrint.swift

@@ -63,6 +63,17 @@ public func print(_ object: some CustomStringConvertible, terminator: StaticStri
   }
 }
 
+func print(_ buf: UnsafeBufferPointer<UInt8>, terminator: StaticString = "\n") {
+  for c in buf {
+    putchar(CInt(c))
+  }
+  var p = terminator.utf8Start
+  while p.pointee != 0 {
+    putchar(CInt(p.pointee))
+    p += 1
+  }
+}
+
 func printCharacters(_ buf: UnsafeRawBufferPointer) {
   for unsafe c in unsafe buf {
     putchar(CInt(c))

stdlib/public/core/EmbeddedRuntime.swift

@@ -527,17 +527,29 @@ public func swift_clearSensitive(buf: UnsafeMutableRawPointer, nbytes: Int) {
 }
 
 @usableFromInline
+@inline(never)
 func _embeddedReportFatalError(prefix: StaticString, message: StaticString) {
   print(prefix, terminator: "")
   if message.utf8CodeUnitCount > 0 { print(": ", terminator: "") }
   print(message)
 }
 
 @usableFromInline
+@inline(never)
 func _embeddedReportFatalErrorInFile(prefix: StaticString, message: StaticString, file: StaticString, line: UInt) {
   print(file, terminator: ":")
   print(line, terminator: ": ")
   print(prefix, terminator: "")
   if message.utf8CodeUnitCount > 0 { print(": ", terminator: "") }
   print(message)
 }
+
+@usableFromInline
+@inline(never)
+func _embeddedReportFatalErrorInFile(prefix: StaticString, message: UnsafeBufferPointer<UInt8>, file: StaticString, line: UInt) {
+  print(file, terminator: ":")
+  print(line, terminator: ": ")
+  print(prefix, terminator: "")
+  if message.count > 0 { print(": ", terminator: "") }
+  print(message)
+}

test/embedded/traps-fatalerror-exec2.swift

@@ -0,0 +1,33 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-clang -x c -c %S/Inputs/unbuffered-putchar.c -o %t/unbuffered-putchar.o
+
+// RUN: %target-build-swift -enable-experimental-feature Embedded -wmo -runtime-compatibility-version none %s -Xlinker %t/unbuffered-putchar.o -o %t/a.out
+// RUN: not --crash %t/a.out 2>&1 | %FileCheck %s --check-prefix=CHECK-MESSAGE
+
+// RUN: %target-build-swift -enable-experimental-feature Embedded -wmo -runtime-compatibility-version none %s -Xlinker %t/unbuffered-putchar.o -o %t/a.out -O
+// RUN: not --crash %t/a.out 2>&1 | %FileCheck %s --check-prefix=CHECK-NOMESSAGE
+
+// RUN: %target-build-swift -enable-experimental-feature Embedded -wmo -runtime-compatibility-version none %s -Xlinker %t/unbuffered-putchar.o -o %t/a.out -Osize
+// RUN: not --crash %t/a.out 2>&1 | %FileCheck %s --check-prefix=CHECK-NOMESSAGE
+
+// RUN: %target-build-swift -enable-experimental-feature Embedded -wmo -runtime-compatibility-version none %s -Xlinker %t/unbuffered-putchar.o -o %t/a.out -O     -assert-config Debug
+// RUN: not --crash %t/a.out 2>&1 | %FileCheck %s --check-prefix=CHECK-MESSAGE
+
+// RUN: %target-build-swift -enable-experimental-feature Embedded -wmo -runtime-compatibility-version none %s -Xlinker %t/unbuffered-putchar.o -o %t/a.out -Osize -assert-config Debug
+// RUN: not --crash %t/a.out 2>&1 | %FileCheck %s --check-prefix=CHECK-MESSAGE
+
+// REQUIRES: swift_in_compiler
+// REQUIRES: executable_test
+// REQUIRES: optimized_stdlib
+// REQUIRES: OS=macosx || OS=linux-gnu
+// REQUIRES: swift_test_mode_optimize_none
+// REQUIRES: swift_feature_Embedded
+
+func testWithInterpolation(i: Int) {
+     fatalError("task failed successfully \(i)")
+     // CHECK-MESSAGE: {{.*}}/traps-fatalerror-exec2.swift:[[@LINE-1]]: Fatal error: task failed successfully 42
+     // CHECK-NOMESSAGE-NOT: Fatal error
+     // CHECK-NOMESSAGE-NOT: task failed successfully 42
+}
+
+testWithInterpolation(i: 42)

test/embedded/traps-fatalerror-ir.swift

@@ -27,3 +27,23 @@ public func test() {
 // CHECK-NOMESSAGE-NEXT:   tail call void @llvm.trap()
 // CHECK-NOMESSAGE-NEXT:   unreachable
 // CHECK-NOMESSAGE-NEXT: }
+
+public func testWithInterpolation(i: Int) {
+     fatalError("task failed successfully \(i)")
+}
+
+// CHECK-MESSAGE: define {{.*}}void @"$e4main21testWithInterpolation1iySi_tF"(i64 %0){{.*}} {
+// CHECK-MESSAGE: entry:
+// CHECK-MESSAGE: task failed successfully
+// CHECK-MESSAGE:   {{.*}}call {{.*}}void @"${{(es17_assertionFailure__|es31_embeddedReportFatalErrorInFile6prefix7message4file4lineys12StaticStringV_SRys5UInt8VGAGSutF)}}
+// CHECK-MESSAGE-SAME: Fatal error
+// CHECK-MESSAGE-SAME: traps-fatalerror-ir.swift
+// CHECK-MESSAGE:   unreachable
+// CHECK-MESSAGE: }
+
+// CHECK-NOMESSAGE:      define {{.*}}void @"$e4main21testWithInterpolation1iySi_tF"(i64 %0){{.*}} {
+// CHECK-NOMESSAGE-NEXT: entry:
+// CHECK-NOMESSAGE-NEXT:   tail call void asm sideeffect "", "n"(i32 0)
+// CHECK-NOMESSAGE-NEXT:   tail call void @llvm.trap()
+// CHECK-NOMESSAGE-NEXT:   unreachable
+// CHECK-NOMESSAGE-NEXT: }