Don't expose unavailable cstdio functions.

[danalbert]

Summary

These aren't available on Android in all configurations.

[ldionne]

libcxx/include/__config

1551

I believe this would be easier to understand if it were instead _LIBCPP_HAS_NO_FGETPOS. The condition would become:

#if defined(__ANDROID__) && defined(__USE_FILE_OFFSET64) && __ANDROID_API < 24

Do you agree?

[danalbert]

libcxx/include/__config

1551

Yep, SGTM. Also corrected __ANDROID__ to __BIONIC__, not that there are any non-android bionic users old enough (or 32-bit enough) for this to be a problem.

[ldionne]

Are there no required changes to the tests as well? I see libcxx/test/std/depr/depr.c.headers/stdio_h.pass.cpp using these declarations.

[danalbert]

Yep, good point. I think we don't run the full libc++ test suite for the broken configuration. Fixed.

[EricWF]

Could we add a .fail.cpp test that ensures when _LIBCPP_HAS_NO_FGETPOS is defined we don't actually have it?

Something like:

using T = decltype(::fgetpos); 
#ifdef _LIBCPP_HAS_NO_FGETPOS
// expected-error@-2 {{no such thing}}
#else
// expected-no-diagnostics
#endif

libcxx/include/__config

1551

Do we really need two macros for this? I would prefer one.

[danalbert]

Add .fail test, merge into single macro.

[danalbert]

(remove some trailing whitespace that snuck in)

[danalbert]

Ping.

[ldionne]

libcxx/test/std/depr/depr.c.headers/no_fgetpos_fsetpos.fail.cpp

1 ↗

(On Diff #250334)

Missing license comment and also // REQUIRES: verify-support.

And I believe this test should be in libcxx/test/libcxx, not in` libcxx/test/std`, cause it is libc++ specific.

[danalbert]

Added missing copyright header and moved into the libcxx specific test directory.

libcxx/include/__config

 #endif
 
 #ifdef _LIBCPP_COMPILER_HAS_BUILTIN_CONSTANT_P
 #define _LIBCPP_BUILTIN_CONSTANT_P(x) __builtin_constant_p(x)
 #else
 #define _LIBCPP_BUILTIN_CONSTANT_P(x) false
 #endif
 
+// Support for _FILE_OFFSET_BITS=64 landed gradually in Android, so the full set
+// of functions used in cstdio may not be available for low API levels when
+// using 64-bit file offsets on LP32.
+#if defined(__BIONIC__) && defined(__USE_FILE_OFFSET64) && __ANDROID_API__ < 24
+#define _LIBCPP_HAS_NO_FGETPOS_FSETPOS
+#endif
+
 #endif // __cplusplus
 
 #endif // _LIBCPP_CONFIG

libcxx/include/cstdio

 using ::fgets;
 using ::fputc;
 using ::fputs;
 using ::getc;
 using ::putc;
 using ::ungetc;
 using ::fread;
 using ::fwrite;
+#ifndef _LIBCPP_HAS_NO_FGETPOS_FSETPOS
 using ::fgetpos;
+#endif
 using ::fseek;
+#ifndef _LIBCPP_HAS_NO_FGETPOS_FSETPOS
 using ::fsetpos;
+#endif
 using ::ftell;
 using ::rewind;
 using ::clearerr;
 using ::feof;
 using ::ferror;
 using ::perror;
 
 #ifndef _LIBCPP_HAS_NO_GLOBAL_FILESYSTEM_NAMESPACE

libcxx/test/libcxx/depr/depr.c.headers/no_fgetpos_fsetpos.fail.cpp

+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: verify-support
+
+#include <cstdio>
+
+using T = decltype(::fgetpos);
+#ifdef _LIBCPP_HAS_NO_FGETPOS_FSETPOS
+// expected-error@-2 {{no such thing}}
+#else
+// expected-no-diagnostics
+#endif
+
+using U = decltype(::fsetpos);
+#ifdef _LIBCPP_HAS_NO_FGETPOS_FSETPOS
+// expected-error@-2 {{no such thing}}
+#else
+// expected-no-diagnostics
+#endif

libcxx/test/std/depr/depr.c.headers/stdio_h.pass.cpp

#if TEST_STD_VER < 14
     static_assert((std::is_same<decltype(gets(cp)), char*>::value), "");
 #endif
     static_assert((std::is_same<decltype(putc(0,fp)), int>::value), "");
     static_assert((std::is_same<decltype(putchar(0)), int>::value), "");
     static_assert((std::is_same<decltype(puts("")), int>::value), "");
     static_assert((std::is_same<decltype(ungetc(0,fp)), int>::value), "");
     static_assert((std::is_same<decltype(fread((void*)0,0,0,fp)), size_t>::value), "");
     static_assert((std::is_same<decltype(fwrite((const void*)arr,1,0,fp)), size_t>::value), "");
+#ifndef _LIBCPP_HAS_NO_FGETPOS_FSETPOS
     static_assert((std::is_same<decltype(fgetpos(fp, &fpos)), int>::value), "");
+#endif
     static_assert((std::is_same<decltype(fseek(fp, 0,0)), int>::value), "");
+#ifndef _LIBCPP_HAS_NO_FGETPOS_FSETPOS
     static_assert((std::is_same<decltype(fsetpos(fp, &fpos)), int>::value), "");
+#endif
     static_assert((std::is_same<decltype(ftell(fp)), long>::value), "");
     static_assert((std::is_same<decltype(rewind(fp)), void>::value), "");
     static_assert((std::is_same<decltype(clearerr(fp)), void>::value), "");
     static_assert((std::is_same<decltype(feof(fp)), int>::value), "");
     static_assert((std::is_same<decltype(ferror(fp)), int>::value), "");
     static_assert((std::is_same<decltype(perror("")), void>::value), "");
 
   return 0;
 }

libcxx/test/std/input.output/file.streams/c.files/cstdio.pass.cpp

int main(int, char**)
     static_assert((std::is_same<decltype(std::fgets(cp,0,fp)), char*>::value), "");
     static_assert((std::is_same<decltype(std::fputc(0,fp)), int>::value), "");
     static_assert((std::is_same<decltype(std::fputs("",fp)), int>::value), "");
     static_assert((std::is_same<decltype(std::getc(fp)), int>::value), "");
     static_assert((std::is_same<decltype(std::putc(0,fp)), int>::value), "");
     static_assert((std::is_same<decltype(std::ungetc(0,fp)), int>::value), "");
     static_assert((std::is_same<decltype(std::fread((void*)0,0,0,fp)), std::size_t>::value), "");
     static_assert((std::is_same<decltype(std::fwrite((const void*)0,0,0,fp)), std::size_t>::value), "");
+#ifndef _LIBCPP_HAS_NO_FGETPOS_FSETPOS
     static_assert((std::is_same<decltype(std::fgetpos(fp, &fpos)), int>::value), "");
+#endif
     static_assert((std::is_same<decltype(std::fseek(fp, 0,0)), int>::value), "");
+#ifndef _LIBCPP_HAS_NO_FGETPOS_FSETPOS
     static_assert((std::is_same<decltype(std::fsetpos(fp, &fpos)), int>::value), "");
+#endif
     static_assert((std::is_same<decltype(std::ftell(fp)), long>::value), "");
     static_assert((std::is_same<decltype(std::rewind(fp)), void>::value), "");
     static_assert((std::is_same<decltype(std::clearerr(fp)), void>::value), "");
     static_assert((std::is_same<decltype(std::feof(fp)), int>::value), "");
     static_assert((std::is_same<decltype(std::ferror(fp)), int>::value), "");
     static_assert((std::is_same<decltype(std::perror("")), void>::value), "");
 
 #ifndef _LIBCPP_HAS_NO_GLOBAL_FILESYSTEM_NAMESPACE