Special case NULL when using printf's %s format

This changes the printf command's %s and %ls formats to special-case
NULL, and print "(null)" for these.  This is PR cli/14977.  This
behavior seems a bit friendlier; I was undecided on whether other
invalid pointers should be handled specially somehow, so for the time
being I've left those out.

gdb/ChangeLog
2018-03-14  Tom Tromey  <tom@tromey.com>

	PR cli/14977:
	* printcmd.c (printf_c_string, printf_wide_c_string): Special case
	for NULL.

gdb/gdbserver/ChangeLog
2018-03-14  Tom Tromey  <tom@tromey.com>

	PR cli/14977:
	* ax.c (ax_printf): Special case for NULL.

gdb/testsuite/ChangeLog
2018-03-14  Tom Tromey  <tom@tromey.com>

	PR cli/14977:
	* gdb.base/printcmds.exp (test_printf): Add printf test of %s with
	a null pointer.
	* gdb.base/wchar.exp: Likewise.

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index da59b39..a62255f 100644 (file)
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,11 @@
 2018-03-14  Tom Tromey  <tom@tromey.com>
 
+       PR cli/14977:
+       * printcmd.c (printf_c_string, printf_wide_c_string): Special case
+       for NULL.
+
+2018-03-14  Tom Tromey  <tom@tromey.com>
+
        PR cli/19918:
        * printcmd.c (printf_pointer): Allow "-" in format.
 

diff --git a/gdb/gdbserver/ChangeLog b/gdb/gdbserver/ChangeLog
index 053cf17..2be87a6 100644 (file)
--- a/gdb/gdbserver/ChangeLog
+++ b/gdb/gdbserver/ChangeLog
@@ -1,3 +1,8 @@
+2018-03-14  Tom Tromey  <tom@tromey.com>
+
+       PR cli/14977:
+       * ax.c (ax_printf): Special case for NULL.
+
 2018-03-08  Simon Marchi  <simon.marchi@polymtl.ca>
 
        * linux-low.c (linux_qxfer_libraries_svr4): Use

diff --git a/gdb/gdbserver/ax.c b/gdb/gdbserver/ax.c
index b42ee54..c754383 100644 (file)
--- a/gdb/gdbserver/ax.c
+++ b/gdb/gdbserver/ax.c
@@ -847,6 +847,11 @@ ax_printf (CORE_ADDR fn, CORE_ADDR chan, const char *format,
            int j;
 
            tem = args[i];
+           if (tem == 0)
+             {
+               printf (current_substring, "(null)");
+               break;
+             }
 
            /* This is a %s argument.  Find the length of the string.  */
            for (j = 0;; j++)

diff --git a/gdb/printcmd.c b/gdb/printcmd.c
index 17c67ee..9fb2e02 100644 (file)
--- a/gdb/printcmd.c
+++ b/gdb/printcmd.c
@@ -2220,6 +2220,11 @@ printf_c_string (struct ui_file *stream, const char *format,
   int j;
 
   tem = value_as_address (value);
+  if (tem == 0)
+    {
+      fprintf_filtered (stream, format, "(null)");
+      return;
+    }
 
   /* This is a %s argument.  Find the length of the string.  */
   for (j = 0;; j++)
@@ -2260,6 +2265,11 @@ printf_wide_c_string (struct ui_file *stream, const char *format,
   gdb_byte *buf = (gdb_byte *) alloca (wcwidth);
 
   tem = value_as_address (value);
+  if (tem == 0)
+    {
+      fprintf_filtered (stream, format, "(null)");
+      return;
+    }
 
   /* This is a %s argument.  Find the length of the string.  */
   for (j = 0;; j += wcwidth)

diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index abac29f..f31f91e 100644 (file)
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,5 +1,12 @@
 2018-03-14  Tom Tromey  <tom@tromey.com>
 
+       PR cli/14977:
+       * gdb.base/printcmds.exp (test_printf): Add printf test of %s with
+       a null pointer.
+       * gdb.base/wchar.exp: Likewise.
+
+2018-03-14  Tom Tromey  <tom@tromey.com>
+
        PR cli/19918:
        * gdb.base/printcmds.exp (test_printf): Add printf test using '-'
        flag.

diff --git a/gdb/testsuite/gdb.base/printcmds.exp b/gdb/testsuite/gdb.base/printcmds.exp
index 56cedb9..635bd62 100644 (file)
--- a/gdb/testsuite/gdb.base/printcmds.exp
+++ b/gdb/testsuite/gdb.base/printcmds.exp
@@ -780,6 +780,9 @@ proc test_printf {} {
     # PR cli/19918.
     gdb_test "printf \"%-16dq\\n\", 0" "0               q"
     gdb_test "printf \"%-16pq\\n\", 0" "\\(nil\\)           q"
+
+    # PR cli/14977.
+    gdb_test "printf \"%s\\n\", 0" "\\(null\\)"
 }
 
 #Test printing DFP values with printf

diff --git a/gdb/testsuite/gdb.base/wchar.exp b/gdb/testsuite/gdb.base/wchar.exp
index 80b6513..a4d9bce 100644 (file)
--- a/gdb/testsuite/gdb.base/wchar.exp
+++ b/gdb/testsuite/gdb.base/wchar.exp
@@ -69,3 +69,6 @@ gdb_test "print repeat" "= L\"A$cent$cent\"\.\.\." \
 
 gdb_test "print repeat_p" "= $hex L\"A$cent$cent\"\.\.\." \
     "print repeat_p (print elements 3)"
+
+# From PR cli/14977, but here because it requires wchar_t.
+gdb_test "printf \"%ls\\n\", 0" "\\(null\\)"