Fix stdin/stdout/stderr for pre-M.

This wasn't an array of pointers, it was an array of structs.
Unfortunately we need a complete type to index into the struct for
stdin/stdout/stderr, so add a phony struct that matches the size and
alignment of `struct __sFILE`. This property is guaranteed by the
static_asserts in libc/bionic/struct_file_test.cpp.

Test: mma
Bug: http://b/30465923
Change-Id: I8ce851dd64a261703bb44f9b5cd23b7caff4dd68

1 files changed, 13 insertions, 0 deletions

diff --git a/libc/stdio/stdio.cpp b/libc/stdio/stdio.cpp
index b709b40c8..b0f5c607f 100644
--- a/libc/stdio/stdio.cpp
+++ b/libc/stdio/stdio.cpp
@@ -848,3 +848,16 @@ int wprintf(const wchar_t* fmt, ...) {
 int wscanf(const wchar_t* fmt, ...) {
   PRINTF_IMPL(vfwscanf(stdin, fmt, ap));
 }
+
+namespace {
+
+namespace phony {
+#include <bits/struct_file.h>
+}
+
+static_assert(sizeof(::__sFILE) == sizeof(phony::__sFILE),
+              "size mismatch between `struct __sFILE` implementation and public stub");
+static_assert(alignof(::__sFILE) == alignof(phony::__sFILE),
+              "alignment mismatch between `struct __sFILE` implementation and public stub");
+
+}