[PATCH 1/2] stack trace support: fix check on symbol name presence

[Thomas De Schampheleire]

From: Thomas De Schampheleire <thomas.de.schampheleire at gmail.com>

The output format of the stack trace is supposed to be different
depending on whether symbol names are available in the build.

However, the check only verified the validity of the pointer, not of the
string pointed to (which could be empty).

This commit fixes the check so that the original output:

mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x5e000
 > /lib/libc-2.10.1.so(_IO_file_doallocate+0x8c) [0x68a38]
 > /lib/libc-2.10.1.so(_IO_doallocbuf+0x6c) [0x78574]
 > /lib/libc-2.10.1.so(_IO_file_overflow+0x184) [0x7763c]
 > /lib/libc-2.10.1.so(_IO_file_xsputn+0x88) [0x76aac]
 > /lib/libc-2.10.1.so(_IO_puts+0xc8) [0x6b64c]
 > /bin/busybox(+0x0) [0x62c60]
 > /bin/busybox(+0x0) [0x4940]
 > /bin/busybox(+0x0) [0x499c]
 > /bin/busybox(+0x0) [0x4e08]
 > /lib/libc-2.10.1.so(__libc_init_first+0x30c) [0x1f84c]
 > /lib/libc-2.10.1.so(__libc_start_main+0xd8) [0x1f9f8]

becomes:

mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x5e000
 > /lib/libc-2.10.1.so(_IO_file_doallocate+0x8c) [0x68a38]
 > /lib/libc-2.10.1.so(_IO_doallocbuf+0x6c) [0x78574]
 > /lib/libc-2.10.1.so(_IO_file_overflow+0x184) [0x7763c]
 > /lib/libc-2.10.1.so(_IO_file_xsputn+0x88) [0x76aac]
 > /lib/libc-2.10.1.so(_IO_puts+0xc8) [0x6b64c]
 > /bin/busybox() [0x62c60]
 > /bin/busybox() [0x4940]
 > /bin/busybox() [0x499c]
 > /bin/busybox() [0x4e08]
 > /lib/libc-2.10.1.so(__libc_init_first+0x30c) [0x1f84c]
 > /lib/libc-2.10.1.so(__libc_start_main+0xd8) [0x1f9f8]

Signed-off-by: Thomas De Schampheleire <thomas.de.schampheleire at gmail.com>
---
 unwind.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/unwind.c b/unwind.c
index 5b06008..6f422a1 100644
--- a/unwind.c
+++ b/unwind.c
@@ -427,7 +427,7 @@ print_call_cb(void *dummy,
 	      unw_word_t function_offset,
 	      unsigned long true_offset)
 {
-	if (symbol_name)
+	if (symbol_name && (symbol_name[0] != '\0'))
 		tprintf(STACK_ENTRY_SYMBOL_FMT);
 	else if (binary_filename)
 		tprintf(STACK_ENTRY_NOSYMBOL_FMT);
-- 
1.7.1