Add a uc_backtrace_buf() functio

include/ucore/ucore_backtrace.h

@@ -2,7 +2,23 @@
 #define UC_BACKTRACE_H_
 
 #define UC_BACTRACE_STDERR uc_backtrace_fd(2)
+#include <stddef.h>
 
+/**
+ * Print a stacktrace to the given file descriptor.
+ *
+ * @param fd filedescriptor to write to.
+ */
 void uc_backtrace_fd(int fd);
+/**
+ * Print a stactrace to the given buffer
+ * (Note that unlike uc_backtrace_fd(), this function
+ * does malloc() call and may fail in a signal handler or
+ * if memory is corrupted.
+ *
+ * @param buf buffer to place the stacktrace in.
+ * @param len length of buffer
+ */
+void uc_backtrace_buf(char *buf, size_t len);
 
 #endif

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);
+}

test/backtrace.c

@@ -1,3 +1,4 @@
+#include <stdio.h>
 #include <ucore/ucore_backtrace.h>
 
 //note , compiling this without -rdynamic does not
@@ -7,9 +8,22 @@ void func2(void)
     uc_backtrace_fd(2);
 }
 
+void func3(void)
+{
+    uc_backtrace_fd(2);
+}
+
+void func4(void)
+{
+    char trace[256];
+    uc_backtrace_buf(trace, sizeof trace);
+    printf("Stacktrace from %s:\n%s", __func__, trace);
+}
+
 void func1(void)
 {
     func2();
+    func4();
 }
 
 int main(int argc, char *argv[])