[libc-commits] [libc] [libc] Embeddeding API for seek and close (PR #221880)
Petr Hosek via libc-commits
libc-commits at lists.llvm.org
Mon Sep 7 22:42:58 PDT 2026
https://github.com/petrhosek created https://github.com/llvm/llvm-project/pull/221880
This change introduces two new symbols to the embedding API hooks: __llvm_libc_stdio_seek and __llvm_libc_stdio_close. These are used to implement fclose, fseek, fseeko, ftell and ftello for baremetal.
The implementation was extracted from #221211.
Authored-by: voltur01
>From 4811e9a0dd7ec09f6cc637754d11b332e66da9d0 Mon Sep 17 00:00:00 2001
From: Petr Hosek <phosek at google.com>
Date: Mon, 7 Sep 2026 22:38:40 -0700
Subject: [PATCH] [libc] Embeddeding API for seek and close
This change introduces two new symbols to the embedding API hooks:
__llvm_libc_stdio_seek and __llvm_libc_stdio_close. These are used to
implement fclose, fseek, fseeko, ftell and ftello for baremetal.
The implementation was extracted from #221211.
Authored-by: voltur01
---
libc/config/baremetal/aarch64/entrypoints.txt | 5 ++
libc/config/baremetal/arm/entrypoints.txt | 5 ++
libc/src/__support/OSUtil/baremetal/io.h | 17 +++++-
libc/src/stdio/baremetal/CMakeLists.txt | 55 +++++++++++++++++++
libc/src/stdio/baremetal/fclose.cpp | 26 +++++++++
libc/src/stdio/baremetal/fseek.cpp | 38 +++++++++++++
libc/src/stdio/baremetal/fseeko.cpp | 37 +++++++++++++
libc/src/stdio/baremetal/ftell.cpp | 38 +++++++++++++
libc/src/stdio/baremetal/ftello.cpp | 38 +++++++++++++
9 files changed, 257 insertions(+), 2 deletions(-)
create mode 100644 libc/src/stdio/baremetal/fclose.cpp
create mode 100644 libc/src/stdio/baremetal/fseek.cpp
create mode 100644 libc/src/stdio/baremetal/fseeko.cpp
create mode 100644 libc/src/stdio/baremetal/ftell.cpp
create mode 100644 libc/src/stdio/baremetal/ftello.cpp
diff --git a/libc/config/baremetal/aarch64/entrypoints.txt b/libc/config/baremetal/aarch64/entrypoints.txt
index 757e4729699d1..114534ce61ae6 100644
--- a/libc/config/baremetal/aarch64/entrypoints.txt
+++ b/libc/config/baremetal/aarch64/entrypoints.txt
@@ -128,6 +128,7 @@ set(TARGET_LIBC_ENTRYPOINTS
libc.src.stdio.feof
libc.src.stdio.ferror
libc.src.stdio.fflush
+ libc.src.stdio.fclose
libc.src.stdio.fgetc
libc.src.stdio.fgets
libc.src.stdio.fprintf
@@ -136,6 +137,10 @@ set(TARGET_LIBC_ENTRYPOINTS
libc.src.stdio.fread
libc.src.stdio.fscanf
libc.src.stdio.fwrite
+ libc.src.stdio.fseek
+ libc.src.stdio.fseeko
+ libc.src.stdio.ftell
+ libc.src.stdio.ftello
libc.src.stdio.getc
libc.src.stdio.getchar
libc.src.stdio.printf
diff --git a/libc/config/baremetal/arm/entrypoints.txt b/libc/config/baremetal/arm/entrypoints.txt
index 13d4f777650f7..50c3313b560a0 100644
--- a/libc/config/baremetal/arm/entrypoints.txt
+++ b/libc/config/baremetal/arm/entrypoints.txt
@@ -128,6 +128,7 @@ set(TARGET_LIBC_ENTRYPOINTS
libc.src.stdio.feof
libc.src.stdio.ferror
libc.src.stdio.fflush
+ libc.src.stdio.fclose
libc.src.stdio.fgetc
libc.src.stdio.fgets
libc.src.stdio.fprintf
@@ -136,6 +137,10 @@ set(TARGET_LIBC_ENTRYPOINTS
libc.src.stdio.fread
libc.src.stdio.fscanf
libc.src.stdio.fwrite
+ libc.src.stdio.fseek
+ libc.src.stdio.fseeko
+ libc.src.stdio.ftell
+ libc.src.stdio.ftello
libc.src.stdio.getc
libc.src.stdio.getchar
libc.src.stdio.printf
diff --git a/libc/src/__support/OSUtil/baremetal/io.h b/libc/src/__support/OSUtil/baremetal/io.h
index 5e691f26060eb..3a61fa8f4535e 100644
--- a/libc/src/__support/OSUtil/baremetal/io.h
+++ b/libc/src/__support/OSUtil/baremetal/io.h
@@ -9,8 +9,9 @@
#ifndef LLVM_LIBC_SRC___SUPPORT_OSUTIL_BAREMETAL_IO_H
#define LLVM_LIBC_SRC___SUPPORT_OSUTIL_BAREMETAL_IO_H
-#include "include/llvm-libc-types/size_t.h"
-#include "include/llvm-libc-types/ssize_t.h"
+#include "hdr/types/off_t.h"
+#include "hdr/types/size_t.h"
+#include "hdr/types/ssize_t.h"
#include "src/__support/CPP/string_view.h"
#include "src/__support/macros/config.h"
@@ -47,10 +48,22 @@ namespace LIBC_NAMESPACE_DECL {
struct __llvm_libc_stdio_cookie;
+// Return the number of bytes read, which can be less than `size` and is zero at
+// end-of-file. On failure, return a negative errno value.
extern "C" ssize_t __llvm_libc_stdio_read(void *cookie, char *buf, size_t size);
+
+// Return the number of bytes written, which can be less than `size`. On
+// failure, return a negative errno value.
extern "C" ssize_t __llvm_libc_stdio_write(void *cookie, const char *buf,
size_t size);
+// Return the resulting absolute file position on success. On failure, return a
+// negative errno value.
+extern "C" off_t __llvm_libc_stdio_seek(void *cookie, off_t offset, int whence);
+
+// Return 0 on success or EOF on failure, matching fclose.
+extern "C" int __llvm_libc_stdio_close(void *cookie);
+
void write_to_stderr(cpp::string_view msg);
} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdio/baremetal/CMakeLists.txt b/libc/src/stdio/baremetal/CMakeLists.txt
index d26cdbb0f9d51..14b7d85db1aef 100644
--- a/libc/src/stdio/baremetal/CMakeLists.txt
+++ b/libc/src/stdio/baremetal/CMakeLists.txt
@@ -10,6 +10,61 @@ add_object_library(
libc.src.__support.OSUtil.osutil
)
+add_entrypoint_object(
+ fclose
+ SRCS fclose.cpp
+ HDRS ../fclose.h
+ DEPENDS
+ libc.src.__support.OSUtil.osutil
+ libc.src.__support.macros.config
+)
+
+add_entrypoint_object(
+ fseek
+ SRCS fseek.cpp
+ HDRS ../fseek.h
+ DEPENDS
+ libc.hdr.errno_macros
+ libc.src.__support.OSUtil.osutil
+ libc.src.__support.macros.config
+ libc.src.errno.errno
+)
+
+add_entrypoint_object(
+ ftell
+ SRCS ftell.cpp
+ HDRS ../ftell.h
+ DEPENDS
+ libc.hdr.errno_macros
+ libc.hdr.stdio_macros
+ libc.src.__support.OSUtil.osutil
+ libc.src.__support.macros.config
+ libc.src.errno.errno
+)
+
+add_entrypoint_object(
+ fseeko
+ SRCS fseeko.cpp
+ HDRS ../fseeko.h
+ DEPENDS
+ libc.hdr.errno_macros
+ libc.src.__support.OSUtil.osutil
+ libc.src.__support.macros.config
+ libc.src.errno.errno
+)
+
+add_entrypoint_object(
+ ftello
+ SRCS ftello.cpp
+ HDRS ../ftello.h
+ DEPENDS
+ libc.hdr.errno_macros
+ libc.hdr.stdio_macros
+ libc.src.__support.OSUtil.osutil
+ libc.src.__support.macros.config
+ libc.src.errno.errno
+)
+
add_header_library(
vfprintf_internal
HDRS
diff --git a/libc/src/stdio/baremetal/fclose.cpp b/libc/src/stdio/baremetal/fclose.cpp
new file mode 100644
index 0000000000000..c7a1e8f7dbc15
--- /dev/null
+++ b/libc/src/stdio/baremetal/fclose.cpp
@@ -0,0 +1,26 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This file contains the bare-metal implementation of fclose.
+///
+//===----------------------------------------------------------------------===//
+
+#include "src/stdio/fclose.h"
+
+#include "src/__support/OSUtil/io.h"
+#include "src/__support/common.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(int, fclose, (::FILE * stream)) {
+ return __llvm_libc_stdio_close(stream);
+}
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdio/baremetal/fseek.cpp b/libc/src/stdio/baremetal/fseek.cpp
new file mode 100644
index 0000000000000..540c3cb70fbe5
--- /dev/null
+++ b/libc/src/stdio/baremetal/fseek.cpp
@@ -0,0 +1,38 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This file contains the bare-metal implementation of fseek.
+///
+//===----------------------------------------------------------------------===//
+
+#include "src/stdio/fseek.h"
+
+#include "hdr/errno_macros.h"
+#include "src/__support/OSUtil/io.h"
+#include "src/__support/common.h"
+#include "src/__support/libc_errno.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(int, fseek, (::FILE * stream, long offset, int whence)) {
+ if (stream == nullptr) {
+ libc_errno = EINVAL;
+ return -1;
+ }
+ off_t result =
+ __llvm_libc_stdio_seek(stream, static_cast<off_t>(offset), whence);
+ if (result < 0) {
+ libc_errno = static_cast<int>(-result);
+ return -1;
+ }
+ return 0;
+}
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdio/baremetal/fseeko.cpp b/libc/src/stdio/baremetal/fseeko.cpp
new file mode 100644
index 0000000000000..42c87aebe6911
--- /dev/null
+++ b/libc/src/stdio/baremetal/fseeko.cpp
@@ -0,0 +1,37 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This file contains the bare-metal implementation of fseeko.
+///
+//===----------------------------------------------------------------------===//
+
+#include "src/stdio/fseeko.h"
+
+#include "hdr/errno_macros.h"
+#include "src/__support/OSUtil/io.h"
+#include "src/__support/common.h"
+#include "src/__support/libc_errno.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(int, fseeko, (::FILE * stream, off_t offset, int whence)) {
+ if (stream == nullptr) {
+ libc_errno = EINVAL;
+ return -1;
+ }
+ off_t result = __llvm_libc_stdio_seek(stream, offset, whence);
+ if (result < 0) {
+ libc_errno = static_cast<int>(-result);
+ return -1;
+ }
+ return 0;
+}
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdio/baremetal/ftell.cpp b/libc/src/stdio/baremetal/ftell.cpp
new file mode 100644
index 0000000000000..8b062d955a4f3
--- /dev/null
+++ b/libc/src/stdio/baremetal/ftell.cpp
@@ -0,0 +1,38 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This file contains the bare-metal implementation of ftell.
+///
+//===----------------------------------------------------------------------===//
+
+#include "src/stdio/ftell.h"
+
+#include "hdr/errno_macros.h"
+#include "hdr/stdio_macros.h"
+#include "src/__support/OSUtil/io.h"
+#include "src/__support/common.h"
+#include "src/__support/libc_errno.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(long, ftell, (::FILE * stream)) {
+ if (stream == nullptr) {
+ libc_errno = EINVAL;
+ return -1;
+ }
+ off_t result = __llvm_libc_stdio_seek(stream, 0, SEEK_CUR);
+ if (result < 0) {
+ libc_errno = static_cast<int>(-result);
+ return -1;
+ }
+ return static_cast<long>(result);
+}
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdio/baremetal/ftello.cpp b/libc/src/stdio/baremetal/ftello.cpp
new file mode 100644
index 0000000000000..0f5db4872a112
--- /dev/null
+++ b/libc/src/stdio/baremetal/ftello.cpp
@@ -0,0 +1,38 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This file contains the bare-metal implementation of ftello.
+///
+//===----------------------------------------------------------------------===//
+
+#include "src/stdio/ftello.h"
+
+#include "hdr/errno_macros.h"
+#include "hdr/stdio_macros.h"
+#include "src/__support/OSUtil/io.h"
+#include "src/__support/common.h"
+#include "src/__support/libc_errno.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(off_t, ftello, (::FILE * stream)) {
+ if (stream == nullptr) {
+ libc_errno = EINVAL;
+ return static_cast<off_t>(-1);
+ }
+ off_t result = __llvm_libc_stdio_seek(stream, 0, SEEK_CUR);
+ if (result < 0) {
+ libc_errno = static_cast<int>(-result);
+ return static_cast<off_t>(-1);
+ }
+ return result;
+}
+
+} // namespace LIBC_NAMESPACE_DECL
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