Headers: Make the type of SIZE_MAX the same as size_t

[dexonsmith]

Summary

size_t is usually defined as unsigned long, but on 64-bit platforms,
stdint.h currently defines SIZE_MAX using "ull" (unsigned long long).
Although this is the same width, it doesn't necessarily have the same
alignment or calling convention. It also triggers printf warnings when
using the format flag "%zu" to print SIZE_MAX.

1. Is there a better way to get the right type for SIZE_MAX?
2. Should we do this for ptrdiff_t as well?

[dexonsmith]

Updated clang/test/Preprocessor/stdint.c, which I missed in the original patch.

[dexonsmith]

+Hal and Richard, a couple of possible reviewers.

[dexonsmith]

Ping.

[rsmith]

This is sadly not a correct change. The relevant requirements (C11 7.20.3/2) on these macros are:

Each instance of these macros shall be replaced by a constant expression suitable for use in #if preprocessing directives, and this expression shall have the same type as would an expression that is an object of the corresponding type converted according to the integer promotions.

The "suitable for use in #if" requirement means that you cannot use a cast, and must instead use a suitable numeric suffix.

Can we instead use __SIZE_MAX__? (And likewise for ptrdiff_t etc.)

clang/test/Preprocessor/stdint.c

1411

Do we really define __SIZE_TYPE__ to unsigned a for some target?

[dexonsmith]

Thanks for the review. __SIZE_MAX__ makes sense to me; and better even if not for the #if requirement. I'll do that for both SIZE_MAX and PTRDIFF_MAX when I get a chance.

clang/test/Preprocessor/stdint.c

1411

This testcase has a #define int a to confirm that we get intmax_t from our token pasting instead of amax_t. unsigned a looks bogus, but I figure such a user is getting what they asked for.

[dexonsmith]

Hmm... presumably, this test should pass:

$ ./bin/clang -nostdinc -isystem ./lib/clang/5.0.0/include -std=c++1z -fsyntax-only t.cpp
t.cpp:3:1: error: static_assert failed
static_assert(__is_same(intptr_t, __INTPTR_TYPE__));
^             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
t.cpp:4:1: error: static_assert failed
static_assert(__is_same(uintptr_t, __UINTPTR_TYPE__));
^             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
2 errors generated.
$ cat t.cpp 
#include <stdint.h>

static_assert(__is_same(intptr_t, __INTPTR_TYPE__));
static_assert(__is_same(uintptr_t, __UINTPTR_TYPE__));

Discovered that it fails (at least for -triple x86_64-apple-macosx10.12.0) while writing tests for an improved patch that covers SIZE_MAX, PTRDIFF_MIN/MAX, UINTPTR_MAX, and INTPTR_MAX, since I was trying:

static_assert(__is_same(__typeof__(INTPTR_MIN), intptr_t));
static_assert(__is_same(__typeof__(INTPTR_MAX), intptr_t));
static_assert(__is_same(__typeof__(UINTPTR_MAX), uintptr_t));
static_assert(__is_same(__typeof__(PTRDIFF_MIN), ptrdiff_t));
static_assert(__is_same(__typeof__(PTRDIFF_MAX), ptrdiff_t));
static_assert(__is_same(__typeof__(SIZE_MAX), size_t));

and the first three assertions all failed.

Is __INTPTR_TYPE__ correct, or is intptr_t? Is it safe to fix the one that's wrong?

[dexonsmith]

Here's an updated patch that uses __SIZE_MAX__ and also handles the other pointer-like integers.

However, the first three static asserts fail, because intptr_t and __INTPTR_TYPE__ are different types (same for uintptr_t and __UINTPTR_TYPE__).

[dexonsmith]

It looks like __INTPTR_TYPE__ was introduced in r64495 in order to help define intptr_t, and then they diverged in r89237.

Changing intptr_t would change the mangling of symbols in libcxx, so that doesn't seem safe. Is it safe to change __INTPTR_TYPE__?

[efriedma]

We normally use stdint.h from the host C library, rather than our own version; this file is only relevant in -ffreestanding mode. So it should be safe to change.

[rsmith]

In D31856#733845, @efriedma wrote:

We normally use stdint.h from the host C library, rather than our own version; this file is only relevant in -ffreestanding mode. So it should be safe to change.

Agreed; r89237 (and nearby changes: r89221, r89224, r89226) are simply wrong. We cannot determine the correct types from the bitwidth alone; there may be multiple types with the relevant width and we must pick the right one. If we back out all of those changes and instead use the correct types as provided by __*_TYPE__, we should be able to remove the __*_WIDTH__ macros too.

[dexonsmith]

Thanks Eli and Richard.

Given that, I've thrown in fixes for INTMAX_MIN, INTMAX_MAX, UINTMAX_MAX, INTMAX_C(), and UINTMAX_C(), as well as fixing the typedefs for intptr_t, uintptr_t, intmax_t, and uintmax_t.

For the static assert type tests, I've explicitly added RUN lines for all the targets tested in test/Preprocessor/stdint.c.

I left out removing __INTPTR_WIDTH__, etc., since I wondered if the CHECK lines for their values were useful on their own. We could kill those in a follow-up though.

[dexonsmith]

clang/test/Headers/stdint-typeof-MINMAX.cpp

1 ↗

(On Diff #96269)

I copied the -ffreestanding out of test/Preprocessor/stdint.c, but I'm wondering if it even serves a purpose here... if not, we could make the RUN lines shorter (and fit 80 columns without breaking in two).

[efriedma]

clang/test/Headers/stdint-typeof-MINMAX.cpp

1 ↗

(On Diff #96269)

Without -ffreestanding, you're testing the contents of /usr/include/stdint.h rather than the compiler's builtin header.

[dexonsmith]

clang/test/Headers/stdint-typeof-MINMAX.cpp

1 ↗

(On Diff #96269)

Ah; I found no difference locally because I have no /usr/include. -v shows me:

ignoring nonexistent directory "/usr/include"

-nostdsysteminc has the same effect as -ffreestanding... but I guess I may as well leave it as is.

[efriedma]

LGTM.

[dexonsmith]

Thanks for the reviews! Committed in r301593.

[dexonsmith]

rsmith: I just noticed you still have a red "X" here (since Phab won't let me "close"). I think I addressed your comments, but let me know if you want me to revert until you have time to look.

clang/lib/Headers/stdint.h

 #define  __INTN_MAX(n)  __stdint_join3( INT, n, _MAX)
 #define __UINTN_MAX(n)  __stdint_join3(UINT, n, _MAX)
 #define  __INTN_C(n, v) __stdint_join3( INT, n, _C(v))
 #define __UINTN_C(n, v) __stdint_join3(UINT, n, _C(v))
 
 /* C99 7.18.2.4 Limits of integer types capable of holding object pointers. */
 /* C99 7.18.3 Limits of other integer types. */
 
-#define  INTPTR_MIN  __INTN_MIN(__INTPTR_WIDTH__)
-#define  INTPTR_MAX  __INTN_MAX(__INTPTR_WIDTH__)
-#define UINTPTR_MAX __UINTN_MAX(__INTPTR_WIDTH__)
-#define PTRDIFF_MIN  __INTN_MIN(__PTRDIFF_WIDTH__)
-#define PTRDIFF_MAX  __INTN_MAX(__PTRDIFF_WIDTH__)
-#define    SIZE_MAX __UINTN_MAX(__SIZE_WIDTH__)
+#define  INTPTR_MIN  (-__INTPTR_MAX__-1)
+#define  INTPTR_MAX    __INTPTR_MAX__
+#define UINTPTR_MAX   __UINTPTR_MAX__
+#define PTRDIFF_MIN (-__PTRDIFF_MAX__-1)
+#define PTRDIFF_MAX   __PTRDIFF_MAX__
+#define    SIZE_MAX      __SIZE_MAX__
 
 /* ISO9899:2011 7.20 (C11 Annex K): Define RSIZE_MAX if __STDC_WANT_LIB_EXT1__
  * is enabled. */
 #if defined(__STDC_WANT_LIB_EXT1__) && __STDC_WANT_LIB_EXT1__ >= 1
 #define   RSIZE_MAX            (SIZE_MAX >> 1)
 #endif
 
 /* C99 7.18.2.5 Limits of greatest-width integer types. */

clang/test/Headers/stdint-typeof-PTR_MIN-PTR_MAX.cpp

+// RUN: %clang_cc1 -std=c++11 -fsyntax-only %s
+#include <stdint.h>
+#include <stddef.h>
+
+static_assert(__is_same(__typeof__(INTPTR_MIN), intptr_t),
+              "INTPTR_MIN should be intptr_t");
+static_assert(__is_same(__typeof__(INTPTR_MAX), intptr_t),
+              "INTPTR_MAX should be intptr_t");
+static_assert(__is_same(__typeof__(UINTPTR_MAX), uintptr_t),
+              "UINTPTR_MAX should be uintptr_t");
+static_assert(__is_same(__typeof__(PTRDIFF_MIN), ptrdiff_t),
+              "PTRDIFF_MIN should be ptrdiff_t");
+static_assert(__is_same(__typeof__(PTRDIFF_MAX), ptrdiff_t),
+              "PTRDIFF_MAX should be ptrdiff_t");
+static_assert(__is_same(__typeof__(SIZE_MAX), size_t),
+              "SIZE_MAX should be size_t");

clang/test/Preprocessor/stdint.c

 // ARM:UINT64_MAX_ 18446744073709551615ULL
 // ARM:INT_LEAST64_MIN_ (-9223372036854775807LL -1)
 // ARM:INT_LEAST64_MAX_ 9223372036854775807LL
 // ARM:UINT_LEAST64_MAX_ 18446744073709551615ULL
 // ARM:INT_FAST64_MIN_ (-9223372036854775807LL -1)
 // ARM:INT_FAST64_MAX_ 9223372036854775807LL
 // ARM:UINT_FAST64_MAX_ 18446744073709551615ULL
 //
-// ARM:INTPTR_MIN_ (-2147483647 -1)
-// ARM:INTPTR_MAX_ 2147483647
-// ARM:UINTPTR_MAX_ 4294967295U
+// ARM:INTPTR_MIN_ (-2147483647L -1)
+// ARM:INTPTR_MAX_ 2147483647L
+// ARM:UINTPTR_MAX_ 4294967295UL
 // ARM:PTRDIFF_MIN_ (-2147483647 -1)
 // ARM:PTRDIFF_MAX_ 2147483647
 // ARM:SIZE_MAX_ 4294967295U
 //
 // ARM:INTMAX_MIN_ (-9223372036854775807LL -1)
 // ARM:INTMAX_MAX_ 9223372036854775807LL
 // ARM:UINTMAX_MAX_ 18446744073709551615ULL
 //

 // MIPS:UINT64_MAX_ 18446744073709551615ULL
 // MIPS:INT_LEAST64_MIN_ (-9223372036854775807LL -1)
 // MIPS:INT_LEAST64_MAX_ 9223372036854775807LL
 // MIPS:UINT_LEAST64_MAX_ 18446744073709551615ULL
 // MIPS:INT_FAST64_MIN_ (-9223372036854775807LL -1)
 // MIPS:INT_FAST64_MAX_ 9223372036854775807LL
 // MIPS:UINT_FAST64_MAX_ 18446744073709551615ULL
 //
-// MIPS:INTPTR_MIN_ (-2147483647 -1)
-// MIPS:INTPTR_MAX_ 2147483647
-// MIPS:UINTPTR_MAX_ 4294967295U
+// MIPS:INTPTR_MIN_ (-2147483647L -1)
+// MIPS:INTPTR_MAX_ 2147483647L
+// MIPS:UINTPTR_MAX_ 4294967295UL
 // MIPS:PTRDIFF_MIN_ (-2147483647 -1)
 // MIPS:PTRDIFF_MAX_ 2147483647
 // MIPS:SIZE_MAX_ 4294967295U
 //
 // MIPS:INTMAX_MIN_ (-9223372036854775807LL -1)
 // MIPS:INTMAX_MAX_ 9223372036854775807LL
 // MIPS:UINTMAX_MAX_ 18446744073709551615ULL
 //

 // PPC64-NETBSD:UINT64_MAX_ 18446744073709551615ULL
 // PPC64-NETBSD:INT_LEAST64_MIN_ (-9223372036854775807LL -1)
 // PPC64-NETBSD:INT_LEAST64_MAX_ 9223372036854775807LL
 // PPC64-NETBSD:UINT_LEAST64_MAX_ 18446744073709551615ULL
 // PPC64-NETBSD:INT_FAST64_MIN_ (-9223372036854775807LL -1)
 // PPC64-NETBSD:INT_FAST64_MAX_ 9223372036854775807LL
 // PPC64-NETBSD:UINT_FAST64_MAX_ 18446744073709551615ULL
 //
-// PPC64-NETBSD:INTPTR_MIN_ (-9223372036854775807LL -1)
-// PPC64-NETBSD:INTPTR_MAX_ 9223372036854775807LL
-// PPC64-NETBSD:UINTPTR_MAX_ 18446744073709551615ULL
-// PPC64-NETBSD:PTRDIFF_MIN_ (-9223372036854775807LL -1)
-// PPC64-NETBSD:PTRDIFF_MAX_ 9223372036854775807LL
-// PPC64-NETBSD:SIZE_MAX_ 18446744073709551615ULL
+// PPC64-NETBSD:INTPTR_MIN_ (-9223372036854775807L -1)
+// PPC64-NETBSD:INTPTR_MAX_ 9223372036854775807L
+// PPC64-NETBSD:UINTPTR_MAX_ 18446744073709551615UL
+// PPC64-NETBSD:PTRDIFF_MIN_ (-9223372036854775807L -1)
+// PPC64-NETBSD:PTRDIFF_MAX_ 9223372036854775807L
+// PPC64-NETBSD:SIZE_MAX_ 18446744073709551615UL
 //
 // PPC64-NETBSD:INTMAX_MIN_ (-9223372036854775807LL -1)
 // PPC64-NETBSD:INTMAX_MAX_ 9223372036854775807LL
 // PPC64-NETBSD:UINTMAX_MAX_ 18446744073709551615ULL
 //
 // PPC64-NETBSD:SIG_ATOMIC_MIN_ (-2147483647 -1)
 // PPC64-NETBSD:SIG_ATOMIC_MAX_ 2147483647
 // PPC64-NETBSD:WINT_MIN_ (-2147483647 -1)

 // PPC:UINT64_MAX_ 18446744073709551615ULL
 // PPC:INT_LEAST64_MIN_ (-9223372036854775807LL -1)
 // PPC:INT_LEAST64_MAX_ 9223372036854775807LL
 // PPC:UINT_LEAST64_MAX_ 18446744073709551615ULL
 // PPC:INT_FAST64_MIN_ (-9223372036854775807LL -1)
 // PPC:INT_FAST64_MAX_ 9223372036854775807LL
 // PPC:UINT_FAST64_MAX_ 18446744073709551615ULL
 //
-// PPC:INTPTR_MIN_ (-2147483647 -1)
-// PPC:INTPTR_MAX_ 2147483647
-// PPC:UINTPTR_MAX_ 4294967295U
-// PPC:PTRDIFF_MIN_ (-2147483647 -1)
-// PPC:PTRDIFF_MAX_ 2147483647
-// PPC:SIZE_MAX_ 4294967295U
+// PPC:INTPTR_MIN_ (-2147483647L -1)
+// PPC:INTPTR_MAX_ 2147483647L
+// PPC:UINTPTR_MAX_ 4294967295UL
+// PPC:PTRDIFF_MIN_ (-2147483647L -1)
+// PPC:PTRDIFF_MAX_ 2147483647L
+// PPC:SIZE_MAX_ 4294967295UL
 //
 // PPC:INTMAX_MIN_ (-9223372036854775807LL -1)
 // PPC:INTMAX_MAX_ 9223372036854775807LL
 // PPC:UINTMAX_MAX_ 18446744073709551615ULL
 //
 // PPC:SIG_ATOMIC_MIN_ (-2147483647 -1)
 // PPC:SIG_ATOMIC_MAX_ 2147483647
 // PPC:WINT_MIN_ (-2147483647 -1)

 // JOIN:typedef uint32_t uintptr_t;
 // JOIN:typedef __INTMAX_TYPE__ intmax_t;
 // JOIN:typedef __UINTMAX_TYPE__ uintmax_t;
 // JOIN:INTPTR_MIN_ (-2147483647 -1)
 // JOIN:INTPTR_MAX_ 2147483647
 // JOIN:UINTPTR_MAX_ 4294967295U
 // JOIN:PTRDIFF_MIN_ (-2147483647 -1)
 // JOIN:PTRDIFF_MAX_ 2147483647
 // JOIN:SIZE_MAX_ 4294967295U
 // JOIN:INTMAX_MIN_ (-9223372036854775807LL -1)
 // JOIN:INTMAX_MAX_ 9223372036854775807LL
 // JOIN:UINTMAX_MAX_ 18446744073709551615ULL
 // JOIN:SIG_ATOMIC_MIN_ (-2147483647 -1)
 // JOIN:SIG_ATOMIC_MAX_ 2147483647
 // JOIN:WINT_MIN_ (-2147483647 -1)
 // JOIN:WINT_MAX_ 2147483647
 // JOIN:WCHAR_MAX_ 2147483647