[libc] Add implementation of errno and define the other macros of errno.h.

Reviewers: stanshebs, alexbrachet

Subscribers: mgorny, MaskRay, tschuett, libc-commits

Tags: #libc-project

Differential Revision: https://reviews.llvm.org/D71094

2 files changed, 39 insertions, 0 deletions

diff --git a/libc/config/linux/api.td b/libc/config/linux/api.td
index e0d4df8324a..7568620b700 100644
--- a/libc/config/linux/api.td
+++ b/libc/config/linux/api.td
@@ -1,5 +1,7 @@
 include "config/public_api.td"
 
+include "spec/linux.td"
+include "spec/posix.td"
 include "spec/stdc.td"
 
 def FloatT : TypeDecl<"float_t"> {
@@ -28,6 +30,13 @@ def NullMacro : MacroDef<"NULL"> {
   }];
 }
 
+def ErrnoMacro : MacroDef<"errno"> {
+  let Defn = [{
+    int *__errno_location();
+    #define errno (*__errno_location())
+  }];
+}
+
 def MathAPI : PublicAPI<"math.h"> {
   let Functions = [
    "acos",
@@ -83,3 +92,22 @@ def StdIOAPI : PublicAPI<"stdio.h"> {
     "snprintf",
   ];
 }
+
+def ErrnoAPI : PublicAPI<"errno.h"> {
+  let Macros = [
+    ErrnoMacro,
+    // We largely depend on linux/errno.h to give us the
+    // various error macro definitions. However, some libc
+    // implementations have chosen to provide definitions
+    // for some of the error macros to account for the ones
+    // missing in linux/errno.h. There is no harm in doing
+    // the same here if we define the macros only when they
+    // are not already defined.
+    MacroDefineIfNot<"ENOTSUP", "EOPNOTSUPP">,
+    MacroDefineIfNot<"ECANCELED", "125">,
+    MacroDefineIfNot<"EOWNERDEAD", "130">,
+    MacroDefineIfNot<"ENOTRECOVERABLE", "131">,
+    MacroDefineIfNot<"ERFKILL", "132">,
+    MacroDefineIfNot<"EHWPOISON", "133">,
+  ];
+}
diff --git a/libc/config/linux/errno.h.in b/libc/config/linux/errno.h.in
new file mode 100644
index 00000000000..793f0f6affd
--- /dev/null
+++ b/libc/config/linux/errno.h.in
@@ -0,0 +1,11 @@
+//===---------------- Linux specific errno.h definitions ------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+%%begin()
+
+#include <linux/errno.h>