Emscripten doesn't provide copy_file_range implementation but it declares
this function in its headers. Meson correctly detects the missing
implementation and unsets HAVE_COPY_FILE_RANGE. However, the stub defined in
file-posix.c causes a type conflict with the declaration from Emscripten
during compilation.

To fix this error, this commit updates the stub implementation in
file-posix.c to exactly match the declaration in Emscripten's headers. The
manpage also aligns with this signature.

Signed-off-by: Kohei Tokunaga <ktokunaga.mail@gmail.com>
---
 block/file-posix.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

V2:
- Removed the Emscripten-specific stub of copy_file_range in
  stubs/emscripten.c. Instead, updated the type of the existing
  copy_file_range stub in block/file-posix.c to match the declaration in the
  Emscripten headers and avoid a compilation error.

diff --git a/block/file-posix.c b/block/file-posix.c
index 69257c0891..2758f31844 100644
--- a/block/file-posix.c
+++ b/block/file-posix.c
@@ -2015,8 +2015,8 @@ static int handle_aiocb_write_zeroes_unmap(void *opaque)
 }
 
 #ifndef HAVE_COPY_FILE_RANGE
-static off_t copy_file_range(int in_fd, off_t *in_off, int out_fd,
-                             off_t *out_off, size_t len, unsigned int flags)
+ssize_t copy_file_range(int in_fd, off_t *in_off, int out_fd,
+                        off_t *out_off, size_t len, unsigned int flags)
 {
 #ifdef __NR_copy_file_range
     return syscall(__NR_copy_file_range, in_fd, in_off, out_fd,
-- 
2.25.1

On Tue, Apr 22, 2025 at 02:27:17PM +0900, Kohei Tokunaga wrote:
> Emscripten doesn't provide copy_file_range implementation but it declares
> this function in its headers. Meson correctly detects the missing
> implementation and unsets HAVE_COPY_FILE_RANGE. However, the stub defined in
> file-posix.c causes a type conflict with the declaration from Emscripten
> during compilation.
> 
> To fix this error, this commit updates the stub implementation in
> file-posix.c to exactly match the declaration in Emscripten's headers. The
> manpage also aligns with this signature.
> 
> Signed-off-by: Kohei Tokunaga <ktokunaga.mail@gmail.com>
> ---
>  block/file-posix.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> V2:
> - Removed the Emscripten-specific stub of copy_file_range in
>   stubs/emscripten.c. Instead, updated the type of the existing
>   copy_file_range stub in block/file-posix.c to match the declaration in the
>   Emscripten headers and avoid a compilation error.

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

On 22/4/25 07:27, Kohei Tokunaga wrote:
> Emscripten doesn't provide copy_file_range implementation but it declares
> this function in its headers. Meson correctly detects the missing
> implementation and unsets HAVE_COPY_FILE_RANGE. However, the stub defined in
> file-posix.c causes a type conflict with the declaration from Emscripten
> during compilation.
> 
> To fix this error, this commit updates the stub implementation in
> file-posix.c to exactly match the declaration in Emscripten's headers. The
> manpage also aligns with this signature.
> 
> Signed-off-by: Kohei Tokunaga <ktokunaga.mail@gmail.com>
> ---
>   block/file-posix.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>