RFA: Building GDB under GLIBC 2.8

["Jim Blandy" <jimb@red-bean.com>]

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The latest version of Ubuntu (Intrepid Ibex) includes a GLIBC that
attaches the warn_unused_result attribute to many C library functions.
 The archer project doesn't use the -Wno-unused flag, so I needed to
fix these to build archer.  It seemed to me that submitting the patch
upstream would be the most helpful thing to do.

The first patch simply adds return value checks.  The second patch
actually removes some code which I think is unnecessary.

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From 95438deda1a4dc5be64d31ed5dd3495060b76147 Mon Sep 17 00:00:00 2001
From: Jim Blandy <jimb@red-bean.com>
Date: Fri, 12 Dec 2008 16:54:06 -0800
Subject: [PATCH] gdb
 	* top.c (gdb_init): Don't set the current directory here; that's
 	already been done in captured_main.

---
 gdb/ChangeLog |    5 +++++
 gdb/top.c     |    3 ---
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/gdb/top.c b/gdb/top.c
index d0ba466..655b7c9 100644
--- a/gdb/top.c
+++ b/gdb/top.c
@@ -1643,9 +1643,6 @@ gdb_init (char *argv0)
 
   /* Run the init function of each source file */
 
-  getcwd (gdb_dirbuf, sizeof (gdb_dirbuf));
-  current_directory = gdb_dirbuf;
-
 #ifdef __MSDOS__
   /* Make sure we return to the original directory upon exit, come
      what may, since the OS doesn't do that for us.  */
-- 
1.5.6.3


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From 708c45c5f92994cd7bc1203f1b804c8d5c1ad90e Mon Sep 17 00:00:00 2001
From: Jim Blandy <jimb@red-bean.com>
Date: Fri, 12 Dec 2008 17:47:01 -0800
Subject: [PATCH] gdb
 	Check return values of functions declared with warn_unused_result
 	attribute in GLIBC 2.8.
 	* cli/cli-cmds.c (pwd_command): Check return value from getcwd.
 	* inflow.c (check_syscall): New function.
 	(new_tty): Use check_syscall to check return values from open and dup.
 	* linux-nat.c (linux_nat_info_proc_cmd): Check return value from fgets.
 	* main.c (captured_main): Call cwd after setting up gdb_stderr;
 	check for errors from getcwd.
 	* mi/mi-cmd-env.c (mi_cmd_env_pwd): Check return value from getcwd.
 	* ui-file.c (stdio_file_write): Check return value from fwrite.
 	(stdio_file_fputs): Check return value from fputs.
 	* utils.c (internal_vproblem): abort if last-ditch error message
 	write fails.

---
 gdb/ChangeLog       |   14 ++++++++++++++
 gdb/cli/cli-cmds.c  |    4 +++-
 gdb/inflow.c        |   22 ++++++++++++++--------
 gdb/linux-nat.c     |    6 ++++--
 gdb/main.c          |   12 +++++++++---
 gdb/mi/mi-cmd-env.c |    5 ++++-
 gdb/ui-file.c       |    6 ++++--
 gdb/utils.c         |    8 +++++++-
 8 files changed, 59 insertions(+), 18 deletions(-)

diff --git a/gdb/cli/cli-cmds.c b/gdb/cli/cli-cmds.c
index 806a68a..b80bdfc 100644
--- a/gdb/cli/cli-cmds.c
+++ b/gdb/cli/cli-cmds.c
@@ -323,7 +323,9 @@ pwd_command (char *args, int from_tty)
 {
   if (args)
     error (_("The \"pwd\" command does not take an argument: %s"), args);
-  getcwd (gdb_dirbuf, sizeof (gdb_dirbuf));
+  if (! getcwd (gdb_dirbuf, sizeof (gdb_dirbuf)))
+    error (_("Error finding name of working directory: %s"),
+           safe_strerror (errno));
 
   if (strcmp (gdb_dirbuf, current_directory) != 0)
     printf_unfiltered (_("Working directory %s\n (canonically %s).\n"),
diff --git a/gdb/inflow.c b/gdb/inflow.c
index e82514e..7ecb5ab 100644
--- a/gdb/inflow.c
+++ b/gdb/inflow.c
@@ -523,6 +523,16 @@ new_tty_prefork (const char *ttyname)
   inferior_thisrun_terminal = ttyname;
 }
 
+static void
+check_syscall (const char *msg, int result)
+{
+  if (result < 0)
+    {
+      print_sys_errmsg (msg, errno);
+      _exit (1);
+    }
+}
+
 void
 new_tty (void)
 {
@@ -549,27 +559,23 @@ new_tty (void)
 
   /* Now open the specified new terminal.  */
   tty = open (inferior_thisrun_terminal, O_RDWR | O_NOCTTY);
-  if (tty == -1)
-    {
-      print_sys_errmsg (inferior_thisrun_terminal, errno);
-      _exit (1);
-    }
+  check_syscall (inferior_thisrun_terminal, tty);
 
   /* Avoid use of dup2; doesn't exist on all systems.  */
   if (tty != 0)
     {
       close (0);
-      dup (tty);
+      check_syscall ("dup'ing tty into fd 0", dup (tty));
     }
   if (tty != 1)
     {
       close (1);
-      dup (tty);
+      check_syscall ("dup'ing tty into fd 1", dup (tty));
     }
   if (tty != 2)
     {
       close (2);
-      dup (tty);
+      check_syscall ("dup'ing tty into fd 2", dup (tty));
     }
 
 #ifdef TIOCSCTTY
diff --git a/gdb/linux-nat.c b/gdb/linux-nat.c
index 913bfec..a829eb8 100644
--- a/gdb/linux-nat.c
+++ b/gdb/linux-nat.c
@@ -3666,8 +3666,10 @@ linux_nat_info_proc_cmd (char *args, int from_tty)
       if ((procfile = fopen (fname1, "r")) != NULL)
 	{
 	  struct cleanup *cleanup = make_cleanup_fclose (procfile);
-	  fgets (buffer, sizeof (buffer), procfile);
-	  printf_filtered ("cmdline = '%s'\n", buffer);
+          if (fgets (buffer, sizeof (buffer), procfile))
+            printf_filtered ("cmdline = '%s'\n", buffer);
+          else
+            warning (_("unable to read '/proc/%lld/cmdline'"), pid);
 	  do_cleanups (cleanup);
 	}
       else
diff --git a/gdb/main.c b/gdb/main.c
index a53002d..a9fd988 100644
--- a/gdb/main.c
+++ b/gdb/main.c
@@ -195,9 +195,6 @@ captured_main (void *data)
   line[0] = '\0';		/* Terminate saved (now empty) cmd line */
   instream = stdin;
 
-  getcwd (gdb_dirbuf, sizeof (gdb_dirbuf));
-  current_directory = gdb_dirbuf;
-
   gdb_stdout = stdio_fileopen (stdout);
   gdb_stderr = stdio_fileopen (stderr);
   gdb_stdlog = gdb_stderr;	/* for moment */
@@ -206,6 +203,15 @@ captured_main (void *data)
   gdb_stdtargerr = gdb_stderr;	/* for moment */
   gdb_stdtargin = gdb_stdin;	/* for moment */
 
+  if (! getcwd (gdb_dirbuf, sizeof (gdb_dirbuf)))
+    /* Don't use *_filtered or warning() (which relies on
+       current_target) until after initialize_all_files(). */
+    fprintf_unfiltered (gdb_stderr,
+                        _("%s: warning: error finding working directory: %s\n"),
+                        argv[0], safe_strerror (errno));
+    
+  current_directory = gdb_dirbuf;
+
   /* Set the sysroot path.  */
 #ifdef TARGET_SYSTEM_ROOT_RELOCATABLE
   gdb_sysroot = make_relative_prefix (argv[0], BINDIR, TARGET_SYSTEM_ROOT);
diff --git a/gdb/mi/mi-cmd-env.c b/gdb/mi/mi-cmd-env.c
index 327ddc5..0103153 100644
--- a/gdb/mi/mi-cmd-env.c
+++ b/gdb/mi/mi-cmd-env.c
@@ -78,7 +78,10 @@ mi_cmd_env_pwd (char *command, char **argv, int argc)
      
   /* Otherwise the mi level is 2 or higher.  */
 
-  getcwd (gdb_dirbuf, sizeof (gdb_dirbuf));
+  if (! getcwd (gdb_dirbuf, sizeof (gdb_dirbuf)))
+    error (_("mi_cmd_env_pwd: error finding name of working directory: %s"),
+           safe_strerror (errno));
+    
   ui_out_field_string (uiout, "cwd", gdb_dirbuf);
 }
 
diff --git a/gdb/ui-file.c b/gdb/ui-file.c
index 9a1d892..2ed304f 100644
--- a/gdb/ui-file.c
+++ b/gdb/ui-file.c
@@ -481,7 +481,8 @@ stdio_file_write (struct ui_file *file, const char *buf, long length_buf)
   if (stdio->magic != &stdio_file_magic)
     internal_error (__FILE__, __LINE__,
 		    _("stdio_file_write: bad magic number"));
-  fwrite (buf, length_buf, 1, stdio->file);
+  if (fwrite (buf, length_buf, 1, stdio->file) != 1)
+    error ("stdio_file_write: %s", safe_strerror (errno));
 }
 
 static void
@@ -491,7 +492,8 @@ stdio_file_fputs (const char *linebuffer, struct ui_file *file)
   if (stdio->magic != &stdio_file_magic)
     internal_error (__FILE__, __LINE__,
 		    _("stdio_file_fputs: bad magic number"));
-  fputs (linebuffer, stdio->file);
+  if (fputs (linebuffer, stdio->file) == EOF)
+    error ("stdio_file_fputs: %s", safe_strerror (errno));
 }
 
 static int
diff --git a/gdb/utils.c b/gdb/utils.c
index d14009f..725f00b 100644
--- a/gdb/utils.c
+++ b/gdb/utils.c
@@ -865,7 +865,13 @@ internal_vproblem (struct internal_problem *problem,
 	abort ();	/* NOTE: GDB has only three calls to abort().  */
       default:
 	dejavu = 3;
-	write (STDERR_FILENO, msg, sizeof (msg));
+        /* Newer GLIBC versions put the warn_unused_result attribute
+           on write, but this is one of those rare cases where
+           ignoring the return value is correct.  Casting to (void)
+           does not fix this problem.  This is the solution suggested
+           at http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25509.  */
+	if (write (STDERR_FILENO, msg, sizeof (msg)) != sizeof (msg))
+          abort ();
 	exit (1);
       }
   }
-- 
1.5.6.3