Revert "[libc] Migrate from baremetal stdio.h to generic stdio.h" (#156371)

Reverts #152748

Author: saturn691

libc/config/baremetal/aarch64/entrypoints.txt

@@ -124,8 +124,6 @@ set(TARGET_LIBC_ENTRYPOINTS
 
     # stdio.h entrypoints
     libc.src.stdio.asprintf
-    libc.src.stdio.fopencookie
-    libc.src.stdio.fprintf
     libc.src.stdio.getchar
     libc.src.stdio.printf
     libc.src.stdio.putchar

libc/config/baremetal/arm/entrypoints.txt

@@ -124,8 +124,6 @@ set(TARGET_LIBC_ENTRYPOINTS
 
     # stdio.h entrypoints
     libc.src.stdio.asprintf
-    libc.src.stdio.fopencookie
-    libc.src.stdio.fprintf
     libc.src.stdio.getchar
     libc.src.stdio.printf
     libc.src.stdio.putchar

libc/config/baremetal/riscv/entrypoints.txt

@@ -124,8 +124,6 @@ set(TARGET_LIBC_ENTRYPOINTS
 
     # stdio.h entrypoints
     libc.src.stdio.asprintf
-    libc.src.stdio.fopencookie
-    libc.src.stdio.fprintf
     libc.src.stdio.getchar
     libc.src.stdio.printf
     libc.src.stdio.putchar

libc/src/__support/File/CMakeLists.txt

@@ -22,18 +22,6 @@ add_object_library(
     libc.src.__support.error_or
 )
 
-add_header_library(
-  cookie_file
-  HDRS
-    cookie_file.h
-  DEPENDS
-    .file
-    libc.hdr.errno_macros
-    libc.hdr.types.cookie_io_functions_t
-    libc.hdr.types.off_t
-    libc.src.__support.CPP.new
-)
-
 add_object_library(
   dir
   SRCS
@@ -53,11 +41,7 @@ endif()
 
 add_subdirectory(${LIBC_TARGET_OS})
 
-if(LIBC_TARGET_OS_IS_BAREMETAL)
-  set(target_file libc.src.__support.File.cookie_file)
-else()
-  set(target_file libc.src.__support.File.${LIBC_TARGET_OS}.file)
-endif()
+set(target_file libc.src.__support.File.${LIBC_TARGET_OS}.file)
 set(target_stdout libc.src.__support.File.${LIBC_TARGET_OS}.stdout)
 set(target_stderr libc.src.__support.File.${LIBC_TARGET_OS}.stderr)
 set(target_stdin libc.src.__support.File.${LIBC_TARGET_OS}.stdin)

libc/src/__support/File/baremetal/CMakeLists.txt

@@ -13,6 +13,45 @@
 
 namespace LIBC_NAMESPACE_DECL {
 
+// These are intended to be provided by the vendor.
+//
+// The signature of these types and functions intentionally match `fopencookie`
+// which allows the following:
+//
+// ```
+// struct __llvm_libc_stdio_cookie { ... };
+// ...
+// struct __llvm_libc_stdio_cookie __llvm_libc_stdin_cookie;
+// cookie_io_functions_t stdin_func = { .read = __llvm_libc_stdio_read };
+// FILE *stdin = fopencookie(&__llvm_libc_stdin_cookie, "r", stdin_func);
+// ...
+// struct __llvm_libc_stdio_cookie __llvm_libc_stdout_cookie;
+// cookie_io_functions_t stdout_func = { .write = __llvm_libc_stdio_write };
+// FILE *stdout = fopencookie(&__llvm_libc_stdout_cookie, "w", stdout_func);
+// ...
+// struct __llvm_libc_stdio_cookie __llvm_libc_stderr_cookie;
+// cookie_io_functions_t stderr_func = { .write = __llvm_libc_stdio_write };
+// FILE *stderr = fopencookie(&__llvm_libc_stderr_cookie, "w", stderr_func);
+// ```
+//
+// At the same time, implementation of functions like `printf` and `scanf` can
+// use `__llvm_libc_stdio_read` and `__llvm_libc_stdio_write` directly to avoid
+// the extra indirection.
+//
+// All three symbols `__llvm_libc_stdin_cookie`, `__llvm_libc_stdout_cookie`,
+// and `__llvm_libc_stderr_cookie` must be provided, even if they don't point
+// at anything.
+
+struct __llvm_libc_stdio_cookie;
+
+extern "C" struct __llvm_libc_stdio_cookie __llvm_libc_stdin_cookie;
+extern "C" struct __llvm_libc_stdio_cookie __llvm_libc_stdout_cookie;
+extern "C" struct __llvm_libc_stdio_cookie __llvm_libc_stderr_cookie;
+
+extern "C" ssize_t __llvm_libc_stdio_read(void *cookie, char *buf, size_t size);
+extern "C" ssize_t __llvm_libc_stdio_write(void *cookie, const char *buf,
+                                           size_t size);
+
 ssize_t read_from_stdin(char *buf, size_t size) {
   return __llvm_libc_stdio_read(static_cast<void *>(&__llvm_libc_stdin_cookie),
                                 buf, size);