[libcxx] [include] Declare __STDC_*_MACROS for C++11 compat in old libc

[mgorny]

Summary

Declare STDC_FORMAT_MACROS, STDC_LIMIT_MACROS and __STDC_CONSTANT_MACROS before including real inttypes.h/stdint.h when the wrapper-header is included in C++11, in order to enable the necessary macros in C99-compliant libc.

The C99 standard defined that the format macros in inttypes.h should be defined by the C++ implementations only when STDC_FORMAT_MACROS is defined, and the limit and constant macros in stdint.h should be defined only when STDC_LIMIT_MACROS and __STDC_CONSTANT_MACROS are defined appropriately. Following this specification, multiple old versions of glibc up to 2.17 do not define those macros by default for C++, rendering the libc++ headers non-compliant to the C++11 standard.

In order to achieve the necessary compliance, STDC_FORMAT_MACROS is defined in wrapped inttypes.h just before including the system inttypes.h, when C++11 or newer is used. Both STDC_LIMIT_MACROS and __STDC_CONSTANT_MACROS are defined in newly-wrapped stdint.h. This fixes the C++11 compliance while preserving the current behavior for C++03.

[EricWF]

Adding reviewers @mclow.lists and @rsmith since he originally wrote the C wrappers.

[rmaprath]

When the <cfoo> headers where split into <cfoo> and <foo.h> headers in D12747, we have left out <cstdint> and <ctime>. I was going to put up a patch to fix this but couldn't get to it. It's good that you are adding <stdint.h>, perhaps you can follow what was done in D12747 and repeat the same for <cstdint>?

You will also need a test for the new header, D12747 has examples.

Hope this helps!

/ Asiri

[EricWF]

include/stdint.h

24 ↗

(On Diff #72434)

Please take a look at how clang/lib/Headers/stdint.h handles forwarding this header, and use a solution similar to that.

27 ↗

(On Diff #72434)

I think we should define __STDC_LIMIT_MACROS and __STDC_CONSTANT_MACROS even if we are in C++03, since we don't provide strict C++03 conformance. However we should still check if __cplusplus is defined.

[mgorny]

In D24903#551890, @rmaprath wrote:

When the <cfoo> headers where split into <cfoo> and <foo.h> headers in D12747, we have left out <cstdint> and <ctime>. I was going to put up a patch to fix this but couldn't get to it. It's good that you are adding <stdint.h>, perhaps you can follow what was done in D12747 and repeat the same for <cstdint>?

I'm sorry but could you be a little more specific, please? I've looked into that diff, and it seems that the cstdint resembles e.g. cinttypes already -- i.e. there's only the include, and 'using' lines there. Or do you mean that I should copy/update the synopsis over to stdint.h?

[mgorny]

In D24903#551890, @rmaprath wrote:

When the <cfoo> headers where split into <cfoo> and <foo.h> headers in D12747, we have left out <cstdint> and <ctime>. I was going to put up a patch to fix this but couldn't get to it. It's good that you are adding <stdint.h>, perhaps you can follow what was done in D12747 and repeat the same for <cstdint>?

You will also need a test for the new header, D12747 has examples.

I see that libcxx already has a pretty complete test for stdint.h.

After consulting the standard, I've shamelessly copied the C part of synopsis to my stdint.h.

[mgorny]

include/stdint.h

25 ↗

(On Diff #72441)

Are you referring to the way __STDC_LIMIT_MACROS etc. is handled there? Or something more?

[rmaprath]

In D24903#551926, @mgorny wrote:

I'm sorry but could you be a little more specific, please? I've looked into that diff, and it seems that the cstdint resembles e.g. cinttypes already -- i.e. there's only the include, and 'using' lines there. Or do you mean that I should copy/update the synopsis over to stdint.h?

My bad, I hadn't actually looked at the current status of <cstdint>, it doesn't seem to need any more work.

/ Asiri

[rmaprath]

In D24903#551938, @mgorny wrote:

I see that libcxx already has a pretty complete test for stdint.h.

Hmm, now I see that too :)

Thanks for the patch.

/ Asiri

[mgorny]

@EricWF, I've copied the additional unset logic from clang. Does this address all of your concerns?

By the way, I think clang misses __STDC_FORMAT_MACROS for inttypes.h. I'll write a patch for that as well, for consistency.

[EricWF]

LGTM. Please remove the LIBCXX macros before committing.

include/stdint.h

118 ↗

(On Diff #72492)

We don't actually need the __STDC_CONSTANT_MACROS_DEFINED_BY_LIBCXX. Please remove before commiting.

[mgorny]

Ok. Thanks for the review.

libcxx/trunk/include/inttypes.h

 */
 
 #include <__config>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
 #endif
 
+/* C99 stdlib (e.g. glibc < 2.18) does not provide format macros needed
+   for C++11 unless __STDC_FORMAT_MACROS is defined
+*/
+#if defined(__cplusplus) && !defined(__STDC_FORMAT_MACROS)
+#   define __STDC_FORMAT_MACROS
+#endif
+
 #include_next <inttypes.h>
 
 #ifdef __cplusplus
 
 #include <stdint.h>
 
 #undef imaxabs
 #undef imaxdiv
 
 #endif // __cplusplus
 
 #endif  // _LIBCPP_INTTYPES_H

libcxx/trunk/include/stdint.h

+// -*- C++ -*-
+//===---------------------------- stdint.h --------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_STDINT_H
+#define _LIBCPP_STDINT_H
+
+/*
+    stdint.h synopsis
+
+Macros:
+
+    INT8_MIN
+    INT16_MIN
+    INT32_MIN
+    INT64_MIN
+
+    INT8_MAX
+    INT16_MAX
+    INT32_MAX
+    INT64_MAX
+
+    UINT8_MAX
+    UINT16_MAX
+    UINT32_MAX
+    UINT64_MAX
+
+    INT_LEAST8_MIN
+    INT_LEAST16_MIN
+    INT_LEAST32_MIN
+    INT_LEAST64_MIN
+
+    INT_LEAST8_MAX
+    INT_LEAST16_MAX
+    INT_LEAST32_MAX
+    INT_LEAST64_MAX
+
+    UINT_LEAST8_MAX
+    UINT_LEAST16_MAX
+    UINT_LEAST32_MAX
+    UINT_LEAST64_MAX
+
+    INT_FAST8_MIN
+    INT_FAST16_MIN
+    INT_FAST32_MIN
+    INT_FAST64_MIN
+
+    INT_FAST8_MAX
+    INT_FAST16_MAX
+    INT_FAST32_MAX
+    INT_FAST64_MAX
+
+    UINT_FAST8_MAX
+    UINT_FAST16_MAX
+    UINT_FAST32_MAX
+    UINT_FAST64_MAX
+
+    INTPTR_MIN
+    INTPTR_MAX
+    UINTPTR_MAX
+
+    INTMAX_MIN
+    INTMAX_MAX
+
+    UINTMAX_MAX
+
+    PTRDIFF_MIN
+    PTRDIFF_MAX
+
+    SIG_ATOMIC_MIN
+    SIG_ATOMIC_MAX
+
+    SIZE_MAX
+
+    WCHAR_MIN
+    WCHAR_MAX
+
+    WINT_MIN
+    WINT_MAX
+
+    INT8_C(value)
+    INT16_C(value)
+    INT32_C(value)
+    INT64_C(value)
+
+    UINT8_C(value)
+    UINT16_C(value)
+    UINT32_C(value)
+    UINT64_C(value)
+
+    INTMAX_C(value)
+    UINTMAX_C(value)
+
+*/
+
+#include <__config>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+/* C99 stdlib (e.g. glibc < 2.18) does not provide macros needed
+   for C++11 unless __STDC_LIMIT_MACROS and __STDC_CONSTANT_MACROS
+   are defined
+*/
+#if defined(__cplusplus) && !defined(__STDC_LIMIT_MACROS)
+#   define __STDC_LIMIT_MACROS
+#endif
+#if defined(__cplusplus) && !defined(__STDC_CONSTANT_MACROS)
+#   define __STDC_CONSTANT_MACROS
+#endif
+
+#include_next <stdint.h>
+
+#endif  // _LIBCPP_STDINT_H