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[RFA 3/3] Special case NULL when using printf's %s format
- From: Tom Tromey <tom at tromey dot com>
- To: gdb-patches at sourceware dot org
- Cc: Tom Tromey <tom at tromey dot com>
- Date: Thu, 15 Feb 2018 13:50:01 -0700
- Subject: [RFA 3/3] Special case NULL when using printf's %s format
- Authentication-results: sourceware.org; auth=none
- References: <20180215205001.337-1-tom@tromey.com>
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
2018-02-14 Tom Tromey <tom@tromey.com>
PR cli/14977:
* printcmd.c (printf_c_string, printf_wide_c_string): Special case
for NULL.
gdb/gdbserver/ChangeLog
2018-02-14 Tom Tromey <tom@tromey.com>
PR cli/14977:
* ax.c (ax_printf): Special case for NULL.
gdb/testsuite/ChangeLog
2018-02-14 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.
---
gdb/ChangeLog | 6 ++++++
gdb/gdbserver/ChangeLog | 5 +++++
gdb/gdbserver/ax.c | 5 +++++
gdb/printcmd.c | 10 ++++++++++
gdb/testsuite/ChangeLog | 7 +++++++
gdb/testsuite/gdb.base/printcmds.exp | 3 +++
gdb/testsuite/gdb.base/wchar.exp | 3 +++
7 files changed, 39 insertions(+)
diff --git a/gdb/gdbserver/ax.c b/gdb/gdbserver/ax.c
index b42ee54c84..c754383df8 100644
--- 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 d2d13895f6..a399ed761b 100644
--- 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/gdb.base/printcmds.exp b/gdb/testsuite/gdb.base/printcmds.exp
index 56cedb908f..635bd621fd 100644
--- 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 80b6513e22..a4d9bce7d0 100644
--- 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\\)"
--
2.13.6