[RFA/gdbserver] Provide dummy readlink on systems where routine is not available.

Joel Brobecker
2012-02-03T11:47:00Z

Hello,

Re: http://www.sourceware.org/ml/gdb-patches/2012-01/msg00931.html

This is an attempt to fix the gdbserver build failure on Windows (MinGW)
hosts due to a the missing `readlink' function.

This patch provides a dummy readlink for systems like Windows which
do not provide one. The dummy version returns -1 and sets errno
to ENOSYS (function not implemented).

gdb/ChangeLog:

* common/gdb_readlink.h, common/gdb_readlink.c: New files.

gdb/gdbserver/ChangeLog:

* configure.ac: Add checks for readlink function and declaration.
* configure: Regenerate.
* config.in: Regenerate.

* Makefile.in (SFILES): Add gdb_readlink.c.
(OBS): Add gdb_readlink.o.
(gdb_readlink_h): New variable.
(gdb_readlink.o): New rule.

Tested on x86-windows with AdaCore's testsuite, although I think
only GNU/Linux targets would use the packet that would use this
routine.

On a side note: If this patch is installed, I think it should be
possible to adjust the inf_child_fileio_readlink code to remove
all #ifdefs. It's a tad trickier because of the dependency on
MAXPATHLEN (I think we should have a portable MAXPATH, GDB_MAXPATH,
and be done with those silly ifdefs and inconsistent uses of MAXPATH
vs MAXPATHLEN vs ...).

OK to commit?
Thanks,
--
Joel

---
gdb/common/gdb_readlink.c | 37 +++++++++++++++++++++++++++++++++++++
gdb/common/gdb_readlink.h | 36 ++++++++++++++++++++++++++++++++++++
gdb/gdbserver/Makefile.in | 9 +++++++--
gdb/gdbserver/config.in | 7 +++++++
gdb/gdbserver/configure | 12 +++++++++++-
gdb/gdbserver/configure.ac | 4 ++--
6 files changed, 100 insertions(+), 5 deletions(-)
create mode 100644 gdb/common/gdb_readlink.c
create mode 100644 gdb/common/gdb_readlink.h

diff --git a/gdb/common/gdb_readlink.c b/gdb/common/gdb_readlink.c
new file mode 100644
index 0000000..2e5c8e3
--- /dev/null
+++ b/gdb/common/gdb_readlink.c
@@ -0,0 +1,37 @@
+/* Copyright (C) 2012 Free Software Foundation, Inc.
+
+ This file is part of GDB.
+
+ This program is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 3 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program. If not, see <http://www.gnu.org/licenses/>. */
+
+#include "gdb_readlink.h"
+
+#ifndef HAVE_READLINK
+#include <errno.h>
+
+/* Provide a dummy version of readlink on the systems that do not
+ support this routine.
+
+ This function return -1 (error) and sets errno to ENOSYS to indicate
+ that this function is not implemented. The caller should be prepared
+ to recover from that. */
+
+ssize_t
+readlink(const char *path, char *buf, size_t bufsiz)
+{
+ errno = EINVAL;
+ return -1;
+}
+#endif
+
diff --git a/gdb/common/gdb_readlink.h b/gdb/common/gdb_readlink.h
new file mode 100644
index 0000000..6acc6fd
--- /dev/null
+++ b/gdb/common/gdb_readlink.h
@@ -0,0 +1,36 @@
+/* Portable access to `readlink'.
+
+ Copyright (C) 2012 Free Software Foundation, Inc.
+
+ This file is part of GDB.
+
+ This program is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 3 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program. If not, see <http://www.gnu.org/licenses/>. */
+
+#ifndef GDB_READLINK_H
+#define GDB_READLINK_H
+
+/* If readlink is available, it should be declared in "unistd.h". */
+#ifdef HAVE_UNISTD_H
+#include <unistd.h>
+#endif
+
+#include <sys/types.h>
+#include "config.h"
+
+#ifndef HAVE_DECL_READLINK
+extern ssize_t readlink (const char *path, char *buf, size_t bufsiz);
+#endif
+
+#endif
+
diff --git a/gdb/gdbserver/Makefile.in b/gdb/gdbserver/Makefile.in
index 6ccf5ae..1e28ef2 100644
--- a/gdb/gdbserver/Makefile.in
+++ b/gdb/gdbserver/Makefile.in
@@ -125,7 +125,8 @@ SFILES= $(srcdir)/gdbreplay.c $(srcdir)/inferiors.c \
$(srcdir)/hostio.c $(srcdir)/hostio-errno.c \
$(srcdir)/common/common-utils.c $(srcdir)/common/xml-utils.c \
$(srcdir)/common/linux-osdata.c $(srcdir)/common/ptid.c \
- $(srcdir)/common/buffer.c
+ $(srcdir)/common/buffer.c \
+ $(srcdir)/common/gdb_readlink.c

DEPFILES = @GDBSERVER_DEPFILES@

@@ -137,7 +138,7 @@ TAGFILES = $(SOURCES) ${HFILES} ${ALLPARAM} ${POSSLIBS}
OBS = inferiors.o regcache.o remote-utils.o server.o signals.o target.o \
utils.o version.o \
mem-break.o hostio.o event-loop.o tracepoint.o \
- xml-utils.o common-utils.o ptid.o buffer.o \
+ xml-utils.o common-utils.o ptid.o buffer.o gdb_readlink.o \
$(XML_BUILTIN) \
$(DEPFILES) $(LIBOBJS)
GDBREPLAY_OBS = gdbreplay.o version.o
@@ -345,6 +346,7 @@ server_h = $(srcdir)/server.h $(regcache_h) config.h $(srcdir)/target.h \
$(srcdir)/../common/gdb_locale.h \
$(ptid_h) \
$(signals_h)
+gdb_readlink_h = $(srcdir)/../common/gdb_readlink.h

linux_low_h = $(srcdir)/linux-low.h

@@ -423,6 +425,9 @@ ptid.o: ../common/ptid.c $(ptid_h)
buffer.o: ../common/buffer.c $(server_h)
$(CC) -c $(CPPFLAGS) $(INTERNAL_CFLAGS) $< -DGDBSERVER

+gdb_readlink.o: ../common/gdb_readlink.c $(gdb_readlink_h)
+ $(CC) -c $(CPPFLAGS) $(INTERNAL_CFLAGS) $< -DGDBSERVER
+
# We build memmem.c without -Werror because this file is not under
# our control. On LynxOS, the compiler generates some warnings
# because str-two-way.h uses a constant (MAX_SIZE) whose definition
diff --git a/gdb/gdbserver/config.in b/gdb/gdbserver/config.in
index a9472ea..b2a356d 100644
--- a/gdb/gdbserver/config.in
+++ b/gdb/gdbserver/config.in
@@ -30,6 +30,10 @@
*/
#undef HAVE_DECL_PERROR

+/* Define to 1 if you have the declaration of `readlink', and to 0 if you
+ don't. */
+#undef HAVE_DECL_READLINK
+
/* Define to 1 if you have the declaration of `strerror', and to 0 if you
don't. */
#undef HAVE_DECL_STRERROR
@@ -128,6 +132,9 @@
/* Define to 1 if you have the `pwrite' function. */
#undef HAVE_PWRITE

+/* Define to 1 if you have the `readlink' function. */
+#undef HAVE_READLINK
+
/* Define to 1 if you have the <sgtty.h> header file. */
#undef HAVE_SGTTY_H

diff --git a/gdb/gdbserver/configure b/gdb/gdbserver/configure
index d92a00f..b014254 100755
--- a/gdb/gdbserver/configure
+++ b/gdb/gdbserver/configure
@@ -4163,7 +4163,7 @@ fi

done

-for ac_func in pread pwrite pread64
+for ac_func in pread pwrite pread64 readlink
do :
as_ac_var=`$as_echo "ac_cv_func_$ac_func" | $as_tr_sh`
ac_fn_c_check_func "$LINENO" "$ac_func" "$as_ac_var"
@@ -4458,6 +4458,16 @@ fi
cat >>confdefs.h <<_ACEOF
#define HAVE_DECL_VSNPRINTF $ac_have_decl
_ACEOF
+ac_fn_c_check_decl "$LINENO" "readlink" "ac_cv_have_decl_readlink" "$ac_includes_default"
+if test "x$ac_cv_have_decl_readlink" = x""yes; then :
+ ac_have_decl=1
+else
+ ac_have_decl=0
+fi
+
+cat >>confdefs.h <<_ACEOF
+#define HAVE_DECL_READLINK $ac_have_decl
+_ACEOF

ac_fn_c_check_type "$LINENO" "socklen_t" "ac_cv_type_socklen_t" "#include <sys/types.h>
diff --git a/gdb/gdbserver/configure.ac b/gdb/gdbserver/configure.ac
index 30666ec..0382430 100644
--- a/gdb/gdbserver/configure.ac
+++ b/gdb/gdbserver/configure.ac
@@ -43,7 +43,7 @@ AC_CHECK_HEADERS(sgtty.h termio.h termios.h sys/reg.h string.h dnl
errno.h fcntl.h signal.h sys/file.h malloc.h dnl
sys/ioctl.h netinet/in.h sys/socket.h netdb.h dnl
netinet/tcp.h arpa/inet.h sys/wait.h)
-AC_CHECK_FUNCS(pread pwrite pread64)
+AC_CHECK_FUNCS(pread pwrite pread64 readlink)
AC_REPLACE_FUNCS(memmem vasprintf vsnprintf)

# Check for UST
@@ -161,7 +161,7 @@ AC_TRY_LINK([
[AC_MSG_RESULT(no)])
fi

-AC_CHECK_DECLS([strerror, perror, memmem, vasprintf, vsnprintf])
+AC_CHECK_DECLS([strerror, perror, memmem, vasprintf, vsnprintf, readlink])

AC_CHECK_TYPES(socklen_t, [], [],
[#include <sys/types.h>
--
1.7.1