Changes between Version 2 and Version 3 of cypress/Programming/CodeDebugging

Timestamp:

08/19/15 21:21:31 (10 years ago)

Author:

fuji

Comment:

—

cypress/Programming/CodeDebugging

@@ -92 +92 @@
 
 == GDB ==
-You can use '''GDB''' on CCS cluster. [[http://www.gnu.org/software/gdb/|GDB]]
+[http://www.gnu.org/software/gdb/]
 
 To debug with '''GDB''', submit an interactive job. [[https://wiki.hpc.tulane.edu/trac/wiki/cypress/using#SubmittingInteractiveJobs|See here]]
@@ -176 +176 @@
 Quit anyway? (y or n) y
 }}}
+
+== valgrid ==
+[http://valgrind.org/]
+
+''Valgrind'' tools can detect many memory management and threading bugs, and profile your programs in detail.
+
+
+=== Detecting Invalid Access  ===
+
+{{{#!c
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+char * foo() {
+  char a[200];
+  strcpy(a, "hello world cup\n");
+  return a;
+}
+
+int main() {
+  char * a = foo();
+  char c = a[0];
+  printf("a[0] = %c\n", c);
+  printf("a = %s\n", a);
+  return 0;
+}
+}}}
+
+Start an interactive session,
+{{{#!bash
+[fuji@cypress2 ~]$ idev -c 1 --gres=mic:0
+Requesting 1 node(s)  task(s) to workshop queue of workshop partition
+1 task(s)/node, 1 cpu(s)/task, mic:0 MIC device(s)/node
+Time: 0 (hr) 60 (min).
+Submitted batch job 52605
+JOBID=52605 begin on cypress01-089
+--> Creating interactive terminal session (login) on node cypress01-089.
+--> You have 0 (hr) 60 (min).
+Last login: Wed Aug 19 21:05:45 2015 from cypress2.cm.cluster
+[fuji@cypress01-089 ~]$
+}}}
+compile and run,
+{{{#!bash
+[fuji@cypress01-089 ~]$ module load intel-psxe/2015-update1
+[fuji@cypress01-089 ~]$ icc off_stack.c
+off_stack.c(8): warning #1251: returning pointer to local variable
+    return a;
+           ^
+
+[fuji@cypress01-089 ~]$ ./a.out
+a[0] = h
+a = hello world cup
+}}}
+
+{{{#!bash
+[fuji@cypress01-089 ~]$ icc -O0 -g off_stack.c
+off_stack.c(8): warning #1251: returning pointer to local variable
+    return a;
+           ^
+
+[fuji@cypress01-089 ~]$ valgrind ./a.out
+==33367== Memcheck, a memory error detector
+==33367== Copyright (C) 2002-2012, and GNU GPL'd, by Julian Seward et al.
+==33367== Using Valgrind-3.8.1 and LibVEX; rerun with -h for copyright info
+==33367== Command: ./a.out
+==33367==
+==33367== Invalid read of size 1
+==33367==    at 0x4005C5: main (off_stack.c:13)
+==33367==  Address 0x7feffdd50 is just below the stack ptr.  To suppress, use: --workaround-gcc296-bugs=yes
+==33367==
+a[0] = h
+a =
+==33367==
+==33367== HEAP SUMMARY:
+==33367==     in use at exit: 0 bytes in 0 blocks
+==33367==   total heap usage: 0 allocs, 0 frees, 0 bytes allocated
+==33367==
+==33367== All heap blocks were freed -- no leaks are possible
+==33367==
+==33367== For counts of detected and suppressed errors, rerun with: -v
+==33367== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 6 from 6)
+[fuji@cypress01-089 ~]$
+}}}
+
+