[PATCH v2] [gdb] Handle EINTR in fgets

[Tom de Vries <tdevries@suse.de>]

Usually, find_charset_names calls iconv -l to get the list of supported
charsets, allowing us to use a charset not in the default list:
...
$ /usr/bin/gdb -q -batch -ex "set charset CP858"
$
...

If the call to iconv -l fails somehow, gdb silently falls back to using the
default list, which gets us instead:
...
$ PATH= /usr/bin/gdb -q -batch -ex "set charset CP858"
Undefined item: "CP858".
$
...

PR gdb/33274 reports that gdb occasionally fails in the same way, because
fgets returns nullptr before the output of iconv -l is read entirely.

We asked the reporter to try out a patch handling errno == EINTR after
fgets returns nullptr, and that fixed the problem.

Fix this by:
- adding an inline function gdb::fgets that handles EINTR, and
- using it instead of fgets.

Tested on x86_64-linux.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=33274
---
 gdb/charset.c               |  3 ++-
 gdb/linux-nat.c             |  3 ++-
 gdb/nat/linux-btrace.c      |  3 ++-
 gdb/nat/linux-osdata.c      | 13 +++++++------
 gdb/nat/linux-procfs.c      |  7 ++++---
 gdbserver/linux-i386-ipa.cc |  3 ++-
 gdbsupport/eintr.h          | 15 +++++++++++++++
 7 files changed, 34 insertions(+), 13 deletions(-)

diff --git a/gdb/charset.c b/gdb/charset.c
index 259362563b2..abf3fe800d2 100644
--- a/gdb/charset.c
+++ b/gdb/charset.c
@@ -25,6 +25,7 @@
 #include "gdbsupport/environ.h"
 #include "arch-utils.h"
 #include <ctype.h>
+#include "gdbsupport/eintr.h"
 
 #ifdef USE_WIN32API
 #include <windows.h>
@@ -842,7 +843,7 @@ find_charset_names (void)
 	  char *start, *r;
 	  int len;
 
-	  r = fgets (buf, sizeof (buf), in);
+	  r = gdb::fgets (buf, sizeof (buf), in);
 	  if (!r)
 	    break;
 	  len = strlen (r);
diff --git a/gdb/linux-nat.c b/gdb/linux-nat.c
index f3179279d92..39f1fb59ae0 100644
--- a/gdb/linux-nat.c
+++ b/gdb/linux-nat.c
@@ -64,6 +64,7 @@
 #include "gdbsupport/scope-exit.h"
 #include "gdbsupport/gdb-sigmask.h"
 #include "gdbsupport/common-debug.h"
+#include "gdbsupport/eintr.h"
 #include <unordered_map>
 
 /* This comment documents high-level logic of this file.
@@ -4301,7 +4302,7 @@ linux_proc_pending_signals (int pid, sigset_t *pending,
   if (procfile == NULL)
     error (_("Could not open %s"), fname);
 
-  while (fgets (buffer, PATH_MAX, procfile.get ()) != NULL)
+  while (gdb::fgets (buffer, PATH_MAX, procfile.get ()) != NULL)
     {
       /* Normal queued signals are on the SigPnd line in the status
 	 file.  However, 2.6 kernels also have a "shared" pending
diff --git a/gdb/nat/linux-btrace.c b/gdb/nat/linux-btrace.c
index 9eadd46c9be..08c7b795a86 100644
--- a/gdb/nat/linux-btrace.c
+++ b/gdb/nat/linux-btrace.c
@@ -26,6 +26,7 @@
 #include "gdbsupport/filestuff.h"
 #include "gdbsupport/scoped_fd.h"
 #include "gdbsupport/scoped_mmap.h"
+#include "gdbsupport/eintr.h"
 
 #include <inttypes.h>
 
@@ -202,7 +203,7 @@ linux_determine_kernel_start (void)
       uint64_t addr;
       int match;
 
-      line = fgets (buffer, sizeof (buffer), file.get ());
+      line = gdb::fgets (buffer, sizeof (buffer), file.get ());
       if (line == NULL)
 	break;
 
diff --git a/gdb/nat/linux-osdata.c b/gdb/nat/linux-osdata.c
index b52a8ed5f36..bfdc26f2795 100644
--- a/gdb/nat/linux-osdata.c
+++ b/gdb/nat/linux-osdata.c
@@ -35,6 +35,7 @@
 #include <dirent.h>
 #include <sys/stat.h>
 #include "gdbsupport/filestuff.h"
+#include "gdbsupport/eintr.h"
 #include <algorithm>
 #include "linux-procfs.h"
 
@@ -562,7 +563,7 @@ linux_xfer_osdata_cpus ()
 
       do
 	{
-	  if (fgets (buf, sizeof (buf), fp.get ()))
+	  if (gdb::fgets (buf, sizeof (buf), fp.get ()))
 	    {
 	      char *key, *value;
 	      int i = 0;
@@ -780,7 +781,7 @@ print_sockets (unsigned short family, int tcp, std::string &buffer)
 
       do
 	{
-	  if (fgets (buf, sizeof (buf), fp.get ()))
+	  if (gdb::fgets (buf, sizeof (buf), fp.get ()))
 	    {
 	      uid_t uid;
 	      unsigned int local_port, remote_port, state;
@@ -961,7 +962,7 @@ linux_xfer_osdata_shm ()
 
       do
 	{
-	  if (fgets (buf, sizeof (buf), fp.get ()))
+	  if (gdb::fgets (buf, sizeof (buf), fp.get ()))
 	    {
 	      key_t key;
 	      uid_t uid, cuid;
@@ -1057,7 +1058,7 @@ linux_xfer_osdata_sem ()
 
       do
 	{
-	  if (fgets (buf, sizeof (buf), fp.get ()))
+	  if (gdb::fgets (buf, sizeof (buf), fp.get ()))
 	    {
 	      key_t key;
 	      uid_t uid, cuid;
@@ -1137,7 +1138,7 @@ linux_xfer_osdata_msg ()
 
       do
 	{
-	  if (fgets (buf, sizeof (buf), fp.get ()))
+	  if (gdb::fgets (buf, sizeof (buf), fp.get ()))
 	    {
 	      key_t key;
 	      PID_T lspid, lrpid;
@@ -1231,7 +1232,7 @@ linux_xfer_osdata_modules ()
 
       do
 	{
-	  if (fgets (buf, sizeof (buf), fp.get ()))
+	  if (gdb::fgets (buf, sizeof (buf), fp.get ()))
 	    {
 	      char *name, *dependencies, *status, *tmp, *saveptr;
 	      unsigned int size;
diff --git a/gdb/nat/linux-procfs.c b/gdb/nat/linux-procfs.c
index d4f9af32bb9..1927a21314e 100644
--- a/gdb/nat/linux-procfs.c
+++ b/gdb/nat/linux-procfs.c
@@ -19,6 +19,7 @@
 #include "linux-procfs.h"
 #include "gdbsupport/filestuff.h"
 #include "gdbsupport/unordered_set.h"
+#include "gdbsupport/eintr.h"
 #include <dirent.h>
 #include <sys/stat.h>
 #include <utility>
@@ -42,7 +43,7 @@ linux_proc_get_int (pid_t lwpid, const char *field, int warn)
       return -1;
     }
 
-  while (fgets (buf, sizeof (buf), status_file.get ()))
+  while (gdb::fgets (buf, sizeof (buf), status_file.get ()))
     if (strncmp (buf, field, field_len) == 0 && buf[field_len] == ':')
       {
 	retval = strtol (&buf[field_len + 1], NULL, 10);
@@ -140,7 +141,7 @@ linux_proc_pid_get_state (pid_t pid, int warn, enum proc_state *state)
     }
 
   have_state = 0;
-  while (fgets (buffer, sizeof (buffer), procfile.get ()) != NULL)
+  while (gdb::fgets (buffer, sizeof (buffer), procfile.get ()) != NULL)
     if (startswith (buffer, "State:"))
       {
 	have_state = 1;
@@ -317,7 +318,7 @@ linux_proc_tid_get_name (ptid_t ptid)
   if (comm_file == NULL)
     return NULL;
 
-  comm_val = fgets (comm_buf, sizeof (comm_buf), comm_file.get ());
+  comm_val = gdb::fgets (comm_buf, sizeof (comm_buf), comm_file.get ());
 
   if (comm_val != NULL)
     {
diff --git a/gdbserver/linux-i386-ipa.cc b/gdbserver/linux-i386-ipa.cc
index 17af6eb3610..7d6b9600c34 100644
--- a/gdbserver/linux-i386-ipa.cc
+++ b/gdbserver/linux-i386-ipa.cc
@@ -21,6 +21,7 @@
 #include <sys/mman.h>
 #include "tracepoint.h"
 #include "gdbsupport/x86-xstate.h"
+#include "gdbsupport/eintr.h"
 #include "arch/i386-linux-tdesc.h"
 #include "arch/x86-linux-tdesc-features.h"
 
@@ -138,7 +139,7 @@ initialize_fast_tracepoint_trampoline_buffer (void)
       return;
     }
 
-  if (fgets (buf, IPA_BUFSIZ, f))
+  if (gdb::fgets (buf, IPA_BUFSIZ, f))
     sscanf (buf, "%llu", &mmap_min_addr);
       
   fclose (f);
diff --git a/gdbsupport/eintr.h b/gdbsupport/eintr.h
index 04f86c8c3df..800cab561b4 100644
--- a/gdbsupport/eintr.h
+++ b/gdbsupport/eintr.h
@@ -116,6 +116,21 @@ write (int fd, const void *buf, size_t count)
   return gdb::handle_eintr (-1, ::write, fd, buf, count);
 }
 
+inline char*
+fgets (char *str, int count, FILE* stream)
+{
+  char *ret;
+
+  do
+    {
+      errno = 0;
+      ret = ::fgets (str, count, stream);
+    }
+  while (ret == nullptr && ferror (stream) && errno == EINTR);
+
+  return ret;
+}
+
 } /* namespace gdb */
 
 #endif /* GDBSUPPORT_EINTR_H */

base-commit: 570f4c0c11910d845c35e94764ded54cb1111583
-- 
2.43.0