stack trace support: fix check on symbol name presence

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@gmail.com>
Acked-by: Masatake YAMATO <yamato@redhat.com>

diff --git a/unwind.c b/unwind.c
index 5b0600833055ce1bf02ad754e3ea62aecae39b2a..6f422a1cf937dfc52cb44d312752605c2fd6d08a 100644 (file)
--- 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);