From ce06ad6901b1d24abb90d6baba5fe01c750ffb4e Mon Sep 17 00:00:00 2001 From: Keith Packard Date: Tue, 15 Dec 2020 17:39:24 +0000 Subject: [PATCH] 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 Signed-off-by: Keith Packard 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. --- libstdc++-v3/acinclude.m4 | 20 ++++++++---- libstdc++-v3/config.h.in | 3 + libstdc++-v3/config/io/basic_file_stdio.cc | 46 +++++++++++++++++++++++++---- libstdc++-v3/configure | 17 +++++++--- 4 files changed, 69 insertions(+), 17 deletions(-) --- a/libstdc++-v3/acinclude.m4 +++ b/libstdc++-v3/acinclude.m4 @@ -2797,24 +2797,30 @@ 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 --- a/libstdc++-v3/config.h.in +++ b/libstdc++-v3/config.h.in @@ -974,6 +974,9 @@ /* Define if sendfile is available in . */ #undef _GLIBCXX_USE_SENDFILE +/* Define to restrict std::__basic_file<> to stdio APIs. */ +#undef _GLIBCXX_USE_STDIO_PURE + /* Define if struct stat has timespec members. */ #undef _GLIBCXX_USE_ST_MTIM --- a/libstdc++-v3/config/io/basic_file_stdio.cc +++ b/libstdc++-v3/config/io/basic_file_stdio.cc @@ -111,13 +111,21 @@ // 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 @@ 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 @@ __basic_file::is_open() const throw () { return _M_cfile != 0; } +#ifndef _GLIBCCXX_USE_STDIO_PURE int __basic_file::fd() throw () { return fileno(_M_cfile); } +#endif __c_file* __basic_file::file() throw () @@ -315,29 +325,47 @@ { 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::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::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; } @@ -350,8 +378,12 @@ if (__off > numeric_limits::max() || __off < numeric_limits::min()) return -1L; +#ifdef _GLIBCXX_USE_STDIO_PURE + return fseek(this->file(), __off, __way); +#else return lseek(this->fd(), __off, __way); #endif +#endif } int @@ -361,7 +393,7 @@ streamsize __basic_file::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 @@ #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(); @@ -395,9 +427,13 @@ 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; } --- a/libstdc++-v3/configure +++ b/libstdc++-v3/configure @@ -16301,7 +16301,7 @@ if test "${enable_cstdio+set}" = set; then : enableval=$enable_cstdio; case "$enableval" in - stdio) ;; + stdio|stdio_posix|stdio_pure) ;; *) as_fn_error $? "Unknown argument to enable/disable cstdio" "$LINENO" 5 ;; esac @@ -16311,16 +16311,23 @@ - # 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 { $as_echo "$as_me:${as_lineno-$LINENO}: result: stdio" >&5 $as_echo "stdio" >&6; } + + if test "x$enable_cstdio" = "xstdio_pure" ; then + +$as_echo "#define _GLIBCXX_USE_STDIO_PURE 1" >>confdefs.h + + fi ;; esac