Add a uc_backtrace_buf() functio

src/ucore_backtrace.c

@@ -1,5 +1,7 @@
 #include <execinfo.h>
 #include <stdio.h>
+#include <stdlib.h>
+#include <ucore/ucore_backtrace.h>
 
 #define MAX_BACKTRACE_SYMBOLS 96
 
@@ -20,4 +22,30 @@ void uc_backtrace_fd(int fd)
     backtrace_symbols_fd(syms, ptrs, fd);
 }
 
+void uc_backtrace_buf(char *buf, size_t len)
+{
+    void *buffer[MAX_BACKTRACE_SYMBOLS];
+    int ptrs;
+    char **lines;
+    size_t remaining = len;
+    int i;
+    
+    ptrs = backtrace(buffer, MAX_BACKTRACE_SYMBOLS);
 
+    buf[0] = 0;
+
+    lines = backtrace_symbols(buffer, ptrs);
+    for (i = 1; i < ptrs; i++) {
+
+        int rc = snprintf(buf, remaining, "%s\n", lines[i]);
+        
+        if (rc <= 0 || (size_t)rc >= remaining) {
+            break;
+        }
+
+        remaining -= rc;
+        buf += rc;
+    }
+
+    free(lines);
+}