[PATCH] D12747: Implement [depr.c.headers]
Richard Smith via cfe-commits
cfe-commits at lists.llvm.org
Thu Oct 8 18:58:06 PDT 2015
On Thu, Oct 8, 2015 at 6:25 PM, Eric Fiselier <eric at efcs.ca> wrote:
> Patch #12 needs revision. A bunch of function definitions were moved
> out of the std namespace and into the global.
> That change is incorrect.
Slightly updated version attached. I should probably explain what's going
on here in more detail:
Per [c.strings]p4-p13, we're supposed to replace C functions of the form
char *foo(const char*);
with a pair of const-correct overloads of the form
char *foo(char *);
const char *foo(const char*);
Now, most C standard libraries will do this for us when included in C++
mode (because it's not possible for the C++ library to fix this up after
the fact). For the cases where we *don't* believe we have such a
considerate C library, we add one declaration to C's overload, to get:
char *foo(char*);
char *foo(const char*)
... which doesn't really help much, but is the closest we can get to the
right set of declarations. The declarations we add just dispatch to the C
declarations.
These new declarations *should* be in the global namespace when including
<string.h>, and it makes sense for us to put them in the global namespace
when including <cstring> (otherwise, that header leaves us with a broken
overload set in the global namespace, containing just one of the two
expected functions).
Anyway, most of the above is a description of what we did before. What's
new here is that we attempt to fix the overload set for both <string.h> and
for <cstring>, not just for the latter. At the end of all these changes,
you'll see that all that the <cfoo> headers do is to include the <foo.h>
header and use using-declarations to pull the names into namespace std;
this is no exception to that pattern.
> On Thu, Oct 8, 2015 at 7:09 PM, Eric Fiselier <eric at efcs.ca> wrote:
> > Patch #11 LGTM. Any reason you removed the "#pragma diagnostic ignored
> > "-Wnonnull"" in test/std/depr/depr.c.headers/stdlib_h.pass.cpp?
> > I would like to leave it in so this test doesn't fail with older clang
> > versions.
> >
> > /Eric
> >
> > On Thu, Oct 8, 2015 at 6:47 PM, Eric Fiselier <eric at efcs.ca> wrote:
> >> Patch #10 LGTM.
> >>
> >> On Thu, Oct 8, 2015 at 4:28 PM, Richard Smith <richard at metafoo.co.uk>
> wrote:
> >>> On Thu, Oct 8, 2015 at 11:50 AM, Marshall Clow <mclow.lists at gmail.com>
> >>> wrote:
> >>>>
> >>>> On Tue, Oct 6, 2015 at 3:57 PM, Richard Smith <richard at metafoo.co.uk>
> >>>> wrote:
> >>>>>
> >>>>> <stddef.h>. This one is tricky:
> >>>>>
> >>>>> 1) There's an (undocumented) interface between the C standard
> library and
> >>>>> this header, where the macros __need_ptrdiff_t, __need_size_t,
> >>>>> __need_wchar_t, __need_NULL, __need_wint_t request just a piece of
> this
> >>>>> header rather than the whole thing. If we see any of those, just go
> straight
> >>>>> to the underlying header.
> >>>>
> >>>>
> >>>> Ok, but in that case we don't get nullptr. I suspect that's OK.
> >>>>
> >>>>>
> >>>>> 2) We probably don't want <stddef.h> to include <cstddef> (for
> >>>>> consistency with other headers)
> >>>>
> >>>>
> >>>> No, we do not! :-)
> >>>>
> >>>>>
> >>>>> , but <stddef.h> must provide a ::nullptr_t (which we don't want
> >>>>> <cstddef> to provide). So neither header includes the other.
> Instead, both
> >>>>> include <__nullptr> for std::nullptr_t, and we duplicate the
> definition of
> >>>>> max_align_t between them, in the case where the compiler's <stddef.h>
> >>>>> doesn't provide it.
> >>>>>
> >>>>> If you prefer, I could make <stddef.h> include <cstddef> to avoid the
> >>>>> duplication of the max_align_t logic.
> >>>>
> >>>>
> >>>> No; this is a minor annoyance, and layer jumping (<stdXXX.h> including
> >>>> <cstdXXX>) is a major annoyance - and I'm pretty sure that that would
> come
> >>>> back to bite us in the future.
> >>>>
> >>>> Looks ok to me.
> >>>
> >>>
> >>> Thanks, everything up to and including patch 09 is now committed.
>
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Index: include/cstring
===================================================================
--- include/cstring (revision 249736)
+++ include/cstring (working copy)
@@ -78,30 +78,13 @@
using ::strncmp;
using ::strcoll;
using ::strxfrm;
-
using ::memchr;
-
using ::strchr;
-
using ::strcspn;
-
using ::strpbrk;
-
using ::strrchr;
-
using ::strspn;
-
using ::strstr;
-
-// MSVCRT, GNU libc and its derivates already have the correct prototype in <string.h> #ifdef __cplusplus
-#if !defined(__GLIBC__) && !defined(_LIBCPP_MSVCRT) && !defined(__sun__) && !defined(_STRING_H_CPLUSPLUS_98_CONFORMANCE_)
-inline _LIBCPP_INLINE_VISIBILITY char* strchr( char* __s, int __c) {return ::strchr(__s, __c);}
-inline _LIBCPP_INLINE_VISIBILITY char* strpbrk( char* __s1, const char* __s2) {return ::strpbrk(__s1, __s2);}
-inline _LIBCPP_INLINE_VISIBILITY char* strrchr( char* __s, int __c) {return ::strrchr(__s, __c);}
-inline _LIBCPP_INLINE_VISIBILITY void* memchr( void* __s, int __c, size_t __n) {return ::memchr(__s, __c, __n);}
-inline _LIBCPP_INLINE_VISIBILITY char* strstr( char* __s1, const char* __s2) {return ::strstr(__s1, __s2);}
-#endif
-
#ifndef _LIBCPP_HAS_NO_THREAD_UNSAFE_C_FUNCTIONS
using ::strtok;
#endif
Index: include/string.h
===================================================================
--- include/string.h (revision 0)
+++ include/string.h (working copy)
@@ -0,0 +1,77 @@
+// -*- C++ -*-
+//===--------------------------- string.h ---------------------------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_STRING_H
+#define _LIBCPP_STRING_H
+
+/*
+ string.h synopsis
+
+Macros:
+
+ NULL
+
+Types:
+
+ size_t
+
+void* memcpy(void* restrict s1, const void* restrict s2, size_t n);
+void* memmove(void* s1, const void* s2, size_t n);
+char* strcpy (char* restrict s1, const char* restrict s2);
+char* strncpy(char* restrict s1, const char* restrict s2, size_t n);
+char* strcat (char* restrict s1, const char* restrict s2);
+char* strncat(char* restrict s1, const char* restrict s2, size_t n);
+int memcmp(const void* s1, const void* s2, size_t n);
+int strcmp (const char* s1, const char* s2);
+int strncmp(const char* s1, const char* s2, size_t n);
+int strcoll(const char* s1, const char* s2);
+size_t strxfrm(char* restrict s1, const char* restrict s2, size_t n);
+const void* memchr(const void* s, int c, size_t n);
+ void* memchr( void* s, int c, size_t n);
+const char* strchr(const char* s, int c);
+ char* strchr( char* s, int c);
+size_t strcspn(const char* s1, const char* s2);
+const char* strpbrk(const char* s1, const char* s2);
+ char* strpbrk( char* s1, const char* s2);
+const char* strrchr(const char* s, int c);
+ char* strrchr( char* s, int c);
+size_t strspn(const char* s1, const char* s2);
+const char* strstr(const char* s1, const char* s2);
+ char* strstr( char* s1, const char* s2);
+char* strtok(char* restrict s1, const char* restrict s2);
+void* memset(void* s, int c, size_t n);
+char* strerror(int errnum);
+size_t strlen(const char* s);
+
+*/
+
+#include <__config>
+#include_next <string.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+#ifdef __cplusplus
+extern "C++" {
+
+// MSVCRT, GNU libc and its derivates already have the correct prototype in <string.h> if __cplusplus is defined
+#if !defined(__GLIBC__) && !defined(_LIBCPP_MSVCRT) && !defined(__sun__) && !defined(_STRING_H_CPLUSPLUS_98_CONFORMANCE_)
+inline _LIBCPP_INLINE_VISIBILITY char* strchr(char* __s, int __c) {return strchr((const char *)__s, __c);}
+inline _LIBCPP_INLINE_VISIBILITY char* strpbrk(char* __s1, const char* __s2) {return strpbrk((const char *)__s1, __s2);}
+inline _LIBCPP_INLINE_VISIBILITY char* strrchr(char* __s, int __c) {return strrchr((const char *)__s, __c);}
+inline _LIBCPP_INLINE_VISIBILITY void* memchr(void* __s, int __c, size_t __n) {return memchr((const void *)__s, __c, __n);}
+inline _LIBCPP_INLINE_VISIBILITY char* strstr(char* __s1, const char* __s2) {return strstr((const char *)__s1, __s2);}
+#endif
+
+}
+#endif
+
+#endif // _LIBCPP_STRING_H
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