[libc] Migrate from baremetal stdio.h to generic stdio.h

This is a follow up to the RFC here:
https://discourse.llvm.org/t/rfc-implementation-of-stdio-on-baremetal/86944

Currently, this is very rough and this PR is only for feedback. This provides
the stdout/stderr/stdin symbols (which now don't have to provided by the user).
This allows the user to have access to all functions, currently I've only
tested `fprintf` but in theory everything that works in the generic folder
should work in the baremetal configuration.

The most important part of the implementation is:
- where we want to put `std*`. Here it is a part of `libc.a`
- if we want it here, what should we set it to? I have aliased
all the streams to a _non-buffered_ stream, which does NOT
require flushing. It is based on the CookieFile that already existed

Author: saturn691

libc/config/baremetal/aarch64/entrypoints.txt

@@ -124,6 +124,8 @@ 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

@@ -124,6 +124,8 @@ 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

@@ -124,6 +124,8 @@ 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

@@ -22,6 +22,20 @@ 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.stdio_macros
+    libc.hdr.types.FILE
+    libc.hdr.types.cookie_io_functions_t
+    libc.src.__support.CPP.new
+    libc.src.__support.File.file
+)
+
 add_object_library(
   dir
   SRCS
@@ -41,10 +55,17 @@ endif()
 
 add_subdirectory(${LIBC_TARGET_OS})
 
-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)
+if(LIBC_TARGET_OS_IS_BAREMETAL)
+  set(target_file libc.src.__support.File.cookie_file)
+  set(target_stdout libc.src.__support.File.${LIBC_TARGET_OS}.stderr)
+  set(target_stderr libc.src.__support.File.${LIBC_TARGET_OS}.stderr)
+  set(target_stdin libc.src.__support.File.${LIBC_TARGET_OS}.stderr)
+else()
+  set(target_file libc.src.__support.File.${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)
+endif()
 
 set(file_targets "${target_file};${target_stdout};${target_stdin};${target_stderr}")
 set(file_aliases "platform_file;platform_stdout;platform_stdin;platform_stderr")

libc/src/__support/OSUtil/baremetal/io.cpp

@@ -13,45 +13,6 @@
 
 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);

libc/src/__support/OSUtil/baremetal/io.h

@@ -14,8 +14,46 @@
 #include "src/__support/CPP/string_view.h"
 #include "src/__support/macros/config.h"
 
+// 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.
 namespace LIBC_NAMESPACE_DECL {
 
+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);
 void write_to_stderr(cpp::string_view msg);
 void write_to_stdout(cpp::string_view msg);

libc/src/stdio/baremetal/CMakeLists.txt

@@ -1,15 +1,3 @@
-add_entrypoint_object(
-  getchar
-  SRCS
-    getchar.cpp
-  HDRS
-    ../getchar.h
-  DEPENDS
-    libc.hdr.stdio_macros
-    libc.src.__support.OSUtil.osutil
-    libc.src.__support.CPP.string_view
-)
-
 add_entrypoint_object(
   remove
   SRCS
@@ -19,87 +7,3 @@ add_entrypoint_object(
   DEPENDS
     libc.include.stdio
 )
-
-add_entrypoint_object(
-  printf
-  SRCS
-    printf.cpp
-  HDRS
-    ../printf.h
-  DEPENDS
-    libc.src.stdio.printf_core.printf_main
-    libc.src.stdio.printf_core.writer
-    libc.src.__support.arg_list
-    libc.src.__support.OSUtil.osutil
-)
-
-add_entrypoint_object(
-  putchar
-  SRCS
-    putchar.cpp
-  HDRS
-    ../putchar.h
-  DEPENDS
-    libc.src.__support.OSUtil.osutil
-    libc.src.__support.CPP.string_view
-)
-
-add_entrypoint_object(
-  puts
-  SRCS
-    puts.cpp
-  HDRS
-    ../puts.h
-  DEPENDS
-    libc.src.__support.OSUtil.osutil
-    libc.src.__support.CPP.string_view
-)
-
-add_header_library(
-  scanf_internal
-  HDRS
-    scanf_internal.h
-  DEPENDS
-    libc.src.stdio.scanf_core.reader
-    libc.src.__support.OSUtil.osutil
-)
-
-add_entrypoint_object(
-  scanf
-  SRCS
-    scanf.cpp
-  HDRS
-    ../scanf.h
-  DEPENDS
-    .scanf_internal
-    libc.include.inttypes
-    libc.src.stdio.scanf_core.scanf_main
-    libc.src.__support.arg_list
-    libc.src.__support.OSUtil.osutil
-)
-
-add_entrypoint_object(
-  vprintf
-  SRCS
-    vprintf.cpp
-  HDRS
-    ../vprintf.h
-  DEPENDS
-    libc.src.stdio.printf_core.printf_main
-    libc.src.stdio.printf_core.writer
-    libc.src.__support.arg_list
-    libc.src.__support.OSUtil.osutil
-)
-
-add_entrypoint_object(
-  vscanf
-  SRCS
-    vscanf.cpp
-  HDRS
-    ../vscanf.h
-  DEPENDS
-    .scanf_internal
-    libc.src.stdio.scanf_core.scanf_main
-    libc.src.__support.arg_list
-    libc.src.__support.OSUtil.osutil
-)