On 10/12/20 12:56 -0800, Keith Packard via Libstdc++ wrote:
Jonathan Wakely <jwak...@redhat.com> writes:
I'll do a bit more testing and push it next week.
That's awesome news. Thanks so much for you help; I'm looking forward to
having real C++ support for my embedded customers!
Pushed to master.
commit 75aee072696a711f3e5b3bd1ab1f2b10fef4c7dd
Author: Keith Packard <kei...@keithp.com>
Date: Tue Dec 15 17:39:24 2020
libstdc++: Support libc with stdio-only I/O in libstdc++
The current libstdc++ basic_file_stdio.cc code assumes a POSIX API
underneath the stdio implementation provided by the host libc. This
means that the host must provide a fairly broad POSIX file API,
including read, write, open, close, lseek and ioctl.
This patch changes basic_file_stdio.cc to only use basic ANSI-C stdio
functions, allowing it to be used with libc implementations like
picolibc which may not have a POSIX operating system underneath.
This is enabled by a new --enable-cstdio=stdio_pure configure option.
Aided-by: Jonathan Wakely <jwak...@redhat.com>
Signed-off-by: Keith Packard <kei...@keithp.com>
libstdc++-v3/ChangeLog:
* acinclude.m4 (GLIBCXX_ENABLE_CSTDIO): Allow "stdio_pure"
option and define _GLIBCXX_USE_PURE_STDIO when it is used. Also
add "stdio_posix" option as an alias for "stdio".
* config/io/basic_file_stdio.cc [_GLIBCXX_USE_PURE_STDIO]: Only
use defined stdio entry points for all I/O operations, without
direct calls to underlying POSIX functions.
* config.h.in: Regenerate.
* configure: Regenerate.
diff --git a/libstdc++-v3/acinclude.m4 b/libstdc++-v3/acinclude.m4
index 61191812c92..df8be3bf805 100644
--- a/libstdc++-v3/acinclude.m4
+++ b/libstdc++-v3/acinclude.m4
@@ -2868,24 +2868,30 @@ AC_DEFUN([GLIBCXX_ENABLE_PARALLEL], [
dnl
-dnl Check for which I/O library to use: stdio, or something specific.
+dnl Check for which I/O library to use: stdio and POSIX, or pure stdio.
dnl
-dnl Default is stdio.
+dnl Default is stdio_posix.
dnl
AC_DEFUN([GLIBCXX_ENABLE_CSTDIO], [
AC_MSG_CHECKING([for underlying I/O to use])
GLIBCXX_ENABLE(cstdio,stdio,[[[=PACKAGE]]],
- [use target-specific I/O package], [permit stdio])
+ [use target-specific I/O package], [permit stdio|stdio_posix|stdio_pure])
- # Now that libio has been removed, you can have any color you want as long
- # as it's black. This is one big no-op until other packages are added, but
- # showing the framework never hurts.
+ # The only available I/O model is based on stdio, via basic_file_stdio.
+ # The default "stdio" is actually "stdio + POSIX" because it uses fdopen(3)
+ # to get a file descriptor and then uses read(3) and write(3) with it.
+ # The "stdio_pure" model doesn't use fdopen and only uses FILE* for I/O.
case ${enable_cstdio} in
- stdio)
+ stdio*)
CSTDIO_H=config/io/c_io_stdio.h
BASIC_FILE_H=config/io/basic_file_stdio.h
BASIC_FILE_CC=config/io/basic_file_stdio.cc
AC_MSG_RESULT(stdio)
+
+ if test "x$enable_cstdio" = "xstdio_pure" ; then
+ AC_DEFINE(_GLIBCXX_USE_STDIO_PURE, 1,
+ [Define to restrict std::__basic_file<> to stdio APIs.])
+ fi
;;
esac
diff --git a/libstdc++-v3/config/io/basic_file_stdio.cc b/libstdc++-v3/config/io/basic_file_stdio.cc
index ba830fb9e97..eedffb017b6 100644
--- a/libstdc++-v3/config/io/basic_file_stdio.cc
+++ b/libstdc++-v3/config/io/basic_file_stdio.cc
@@ -111,13 +111,21 @@ namespace
// Wrapper handling partial write.
static std::streamsize
+#ifdef _GLIBCXX_USE_STDIO_PURE
+ xwrite(FILE *__file, const char* __s, std::streamsize __n)
+#else
xwrite(int __fd, const char* __s, std::streamsize __n)
+#endif
{
std::streamsize __nleft = __n;
for (;;)
{
+#ifdef _GLIBCXX_USE_STDIO_PURE
+ const std::streamsize __ret = fwrite(__file, 1, __nleft, __file);
+#else
const std::streamsize __ret = write(__fd, __s, __nleft);
+#endif
if (__ret == -1L && errno == EINTR)
continue;
if (__ret == -1L)
@@ -133,7 +141,7 @@ namespace
return __n - __nleft;
}
-#ifdef _GLIBCXX_HAVE_WRITEV
+#if defined(_GLIBCXX_HAVE_WRITEV) && !defined(_GLIBCXX_USE_STDIO_PURE)
// Wrapper handling partial writev.
static std::streamsize
xwritev(int __fd, const char* __s1, std::streamsize __n1,
@@ -286,9 +294,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
__basic_file<char>::is_open() const throw ()
{ return _M_cfile != 0; }
+#ifndef _GLIBCCXX_USE_STDIO_PURE
int
__basic_file<char>::fd() throw ()
{ return fileno(_M_cfile); }
+#endif
__c_file*
__basic_file<char>::file() throw ()
@@ -315,28 +325,46 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
{
streamsize __ret;
do
+#ifdef _GLIBCXX_USE_STDIO_PURE
+ __ret = fread(__s, 1, __n, this->file());
+#else
__ret = read(this->fd(), __s, __n);
+#endif
while (__ret == -1L && errno == EINTR);
return __ret;
}
streamsize
__basic_file<char>::xsputn(const char* __s, streamsize __n)
- { return xwrite(this->fd(), __s, __n); }
+ {
+#ifdef _GLIBCXX_USE_STDIO_PURE
+ return xwrite(this->file(), __s, __n);
+#else
+ return xwrite(this->fd(), __s, __n);
+#endif
+ }
streamsize
__basic_file<char>::xsputn_2(const char* __s1, streamsize __n1,
const char* __s2, streamsize __n2)
{
streamsize __ret = 0;
-#ifdef _GLIBCXX_HAVE_WRITEV
+#if defined(_GLIBCXX_HAVE_WRITEV) && !defined(_GLIBCXX_USE_STDIO_PURE)
__ret = xwritev(this->fd(), __s1, __n1, __s2, __n2);
#else
if (__n1)
+#ifdef _GLIBCXX_USE_STDIO_PURE
+ __ret = xwrite(this->file(), __s1, __n1);
+#else
__ret = xwrite(this->fd(), __s1, __n1);
+#endif
if (__ret == __n1)
+#ifdef _GLIBCXX_USE_STDIO_PURE
+ __ret += xwrite(this->file(), __s2, __n2);
+#else
__ret += xwrite(this->fd(), __s2, __n2);
+#endif
#endif
return __ret;
}
@@ -350,7 +378,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
if (__off > numeric_limits<off_t>::max()
|| __off < numeric_limits<off_t>::min())
return -1L;
+#ifdef _GLIBCXX_USE_STDIO_PURE
+ return fseek(this->file(), __off, __way);
+#else
return lseek(this->fd(), __off, __way);
+#endif
#endif
}
@@ -361,7 +393,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
streamsize
__basic_file<char>::showmanyc()
{
-#ifndef _GLIBCXX_NO_IOCTL
+#if !defined(_GLIBCXX_NO_IOCTL) && !defined(_GLIBCXX_USE_STDIO_PURE)
#ifdef FIONREAD
// Pipes and sockets.
int __num = 0;
@@ -371,7 +403,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
#endif
#endif
-#ifdef _GLIBCXX_HAVE_POLL
+#if defined(_GLIBCXX_HAVE_POLL) && !defined(_GLIBCXX_USE_STDIO_PURE)
// Cheap test.
struct pollfd __pfd[1];
__pfd[0].fd = this->fd();
@@ -395,8 +427,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
struct stat __buffer;
const int __err = fstat(this->fd(), &__buffer);
if (!__err && _GLIBCXX_ISREG(__buffer.st_mode))
+#ifdef _GLIBCXX_USE_STDIO_PURE
+ return __buffer.st_size - fseek(this->file(), 0, ios_base::cur);
+#else
return __buffer.st_size - lseek(this->fd(), 0, ios_base::cur);
#endif
+#endif
#endif
return 0;
}
