Don't expose unavailable cstdio functions.

Summary: These aren't available on Android in all configurations.

Reviewers: EricWF, mclow.lists, #libc, ldionne

Reviewed By: EricWF, #libc, ldionne

Subscribers: broadwaylamb, dexonsmith, ldionne, krytarowski, libcxx-commits

Tags: #libc

Differential Revision: https://reviews.llvm.org/D76093

libcxx/include/__config

@@ -1545,6 +1545,13 @@ _LIBCPP_FUNC_VIS extern "C" void __sanitizer_annotate_contiguous_container(
 #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

@@ -131,9 +131,13 @@ 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;

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

@@ -0,0 +1,25 @@
+//===----------------------------------------------------------------------===//
+//
+// 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

@@ -156,9 +156,13 @@ int main(int, char**)
     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), "");

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

@@ -120,9 +120,13 @@ int main(int, char**)
     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), "");