[libc] Add baremetal printf (#94078)

For baremetal targets that don't support FILE, this version of printf
just writes directly to a function provided by a vendor. To do this both
printf and vprintf were moved to /generic (vprintf since they need the
same flags and cmake gets funky about setting variables in one file and
reading them in another).

Author: michaelrj-google

libc/src/stdio/CMakeLists.txt

@@ -159,29 +159,6 @@ add_entrypoint_object(
     libc.src.stdio.printf_core.writer
 )
 
-list(APPEND printf_deps
-      libc.src.__support.arg_list
-      libc.src.stdio.printf_core.vfprintf_internal
-)
-
-if(LLVM_LIBC_FULL_BUILD)
-  list(APPEND printf_deps
-      libc.src.__support.File.file
-      libc.src.__support.File.platform_file
-      libc.src.__support.File.platform_stdout
-  )
-endif()
-
-add_entrypoint_object(
-  printf
-  SRCS
-    printf.cpp
-  HDRS
-    printf.h
-  DEPENDS
-    ${printf_deps}
-)
-
 add_entrypoint_object(
   fprintf
   SRCS
@@ -215,16 +192,6 @@ add_entrypoint_object(
     libc.src.stdio.printf_core.writer
 )
 
-add_entrypoint_object(
-  vprintf
-  SRCS
-    vprintf.cpp
-  HDRS
-    vprintf.h
-  DEPENDS
-    ${printf_deps}
-)
-
 add_entrypoint_object(
   vfprintf
   SRCS
@@ -286,6 +253,7 @@ add_stdio_entrypoint_object(fwrite)
 add_stdio_entrypoint_object(fputc)
 add_stdio_entrypoint_object(putc)
 add_stdio_entrypoint_object(putchar)
+add_stdio_entrypoint_object(printf)
 add_stdio_entrypoint_object(fgetc)
 add_stdio_entrypoint_object(fgetc_unlocked)
 add_stdio_entrypoint_object(getc)
@@ -297,3 +265,4 @@ add_stdio_entrypoint_object(ungetc)
 add_stdio_entrypoint_object(stdin)
 add_stdio_entrypoint_object(stdout)
 add_stdio_entrypoint_object(stderr)
+add_stdio_entrypoint_object(vprintf)

libc/src/stdio/baremetal/CMakeLists.txt

@@ -7,3 +7,15 @@ 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/stdio/baremetal/printf.cpp

@@ -0,0 +1,57 @@
+//===-- Implementation of printf for baremetal ------------------*- C++ -*-===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/stdio/printf.h"
+#include "src/__support/arg_list.h"
+#include "src/stdio/printf_core/core_structs.h"
+#include "src/stdio/printf_core/printf_main.h"
+#include "src/stdio/printf_core/writer.h"
+
+#include <stdarg.h>
+
+// TODO(https://github.com/llvm/llvm-project/issues/94685) unify baremetal hooks
+
+// This is intended to be provided by the vendor.
+extern "C" size_t __llvm_libc_raw_write(const char *s, size_t size);
+
+namespace LIBC_NAMESPACE {
+
+namespace {
+
+LIBC_INLINE int raw_write_hook(cpp::string_view new_str, void *) {
+  size_t written = __llvm_libc_raw_write(new_str.data(), new_str.size());
+  if (written != new_str.size())
+    return printf_core::FILE_WRITE_ERROR;
+  return printf_core::WRITE_OK;
+}
+
+} // namespace
+
+LLVM_LIBC_FUNCTION(int, printf, (const char *__restrict format, ...)) {
+  va_list vlist;
+  va_start(vlist, format);
+  internal::ArgList args(vlist); // This holder class allows for easier copying
+                                 // and pointer semantics, as well as handling
+                                 // destruction automatically.
+  va_end(vlist);
+  constexpr size_t BUFF_SIZE = 1024;
+  char buffer[BUFF_SIZE];
+
+  printf_core::WriteBuffer wb(buffer, BUFF_SIZE, &raw_write_hook, nullptr);
+  printf_core::Writer writer(&wb);
+
+  int retval = printf_core::printf_main(&writer, format, args);
+
+  int flushval = wb.overflow_write("");
+  if (flushval != printf_core::WRITE_OK)
+    retval = flushval;
+
+  return retval;
+}
+
+} // namespace LIBC_NAMESPACE

libc/src/stdio/generic/CMakeLists.txt

@@ -363,6 +363,39 @@ add_entrypoint_object(
     libc.src.__support.File.platform_file
 )
 
+list(APPEND printf_deps
+      libc.src.__support.arg_list
+      libc.src.stdio.printf_core.vfprintf_internal
+)
+
+if(LLVM_LIBC_FULL_BUILD)
+  list(APPEND printf_deps
+      libc.src.__support.File.file
+      libc.src.__support.File.platform_file
+      libc.src.__support.File.platform_stdout
+  )
+endif()
+
+add_entrypoint_object(
+  printf
+  SRCS
+    printf.cpp
+  HDRS
+    ../printf.h
+  DEPENDS
+    ${printf_deps}
+)
+
+add_entrypoint_object(
+  vprintf
+  SRCS
+    vprintf.cpp
+  HDRS
+    ../vprintf.h
+  DEPENDS
+    ${printf_deps}
+)
+
 add_entrypoint_object(
   fgets
   SRCS