⇒  valgrind --leak-check=full ./tst_free_basic
==10686== Memcheck, a memory error detector
==10686== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==10686== Using Valgrind-3.13.0 and LibVEX; rerun with -h for copyright info
==10686== Command: ./tst_free_basic
==10686==
a 0x522d040
==10686== Invalid read of size 1
==10686==    at 0x4C32CF2: strlen (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==10686==    by 0x4E994D2: vfprintf (vfprintf.c:1643)
==10686==    by 0x4EC490F: vsnprintf (vsnprintf.c:114)
==10686==    by 0x108A3E: strdup_printf (tst_free_basic.c:22)
==10686==    by 0x108B09: w_strdup_printf (tst_free_basic.c:34)
==10686==    by 0x108B9A: main (tst_free_basic.c:46)
==10686==  Address 0x522d040 is 0 bytes inside a block of size 17 free'd
==10686==    at 0x4C30D3B: free (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==10686==    by 0x108B7D: main (tst_free_basic.c:44)
==10686==  Block was alloc'd at
==10686==    at 0x4C2FB0F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==10686==    by 0x1089FB: strdup_printf (tst_free_basic.c:17)
==10686==    by 0x108B09: w_strdup_printf (tst_free_basic.c:34)
==10686==    by 0x108B55: main (tst_free_basic.c:42)
==10686==
==10686== Invalid read of size 1
==10686==    at 0x4C32D04: strlen (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==10686==    by 0x4E994D2: vfprintf (vfprintf.c:1643)
==10686==    by 0x4EC490F: vsnprintf (vsnprintf.c:114)
==10686==    by 0x108A3E: strdup_printf (tst_free_basic.c:22)
==10686==    by 0x108B09: w_strdup_printf (tst_free_basic.c:34)
==10686==    by 0x108B9A: main (tst_free_basic.c:46)
==10686==  Address 0x522d041 is 1 bytes inside a block of size 17 free'd
==10686==    at 0x4C30D3B: free (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==10686==    by 0x108B7D: main (tst_free_basic.c:44)
==10686==  Block was alloc'd at
==10686==    at 0x4C2FB0F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==10686==    by 0x1089FB: strdup_printf (tst_free_basic.c:17)
==10686==    by 0x108B09: w_strdup_printf (tst_free_basic.c:34)
==10686==    by 0x108B55: main (tst_free_basic.c:42)
==10686==
==10686== Invalid read of size 1
==10686==    at 0x4ECA532: _IO_default_xsputn (genops.c:412)
==10686==    by 0x4E98FEA: vfprintf (vfprintf.c:1643)
==10686==    by 0x4EC490F: vsnprintf (vsnprintf.c:114)
==10686==    by 0x108A3E: strdup_printf (tst_free_basic.c:22)
==10686==    by 0x108B09: w_strdup_printf (tst_free_basic.c:34)
==10686==    by 0x108B9A: main (tst_free_basic.c:46)
==10686==  Address 0x522d040 is 0 bytes inside a block of size 17 free'd
==10686==    at 0x4C30D3B: free (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==10686==    by 0x108B7D: main (tst_free_basic.c:44)
==10686==  Block was alloc'd at
==10686==    at 0x4C2FB0F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==10686==    by 0x1089FB: strdup_printf (tst_free_basic.c:17)
==10686==    by 0x108B09: w_strdup_printf (tst_free_basic.c:34)
==10686==    by 0x108B55: main (tst_free_basic.c:42)
==10686==
==10686== Invalid read of size 1
==10686==    at 0x4ECA540: _IO_default_xsputn (genops.c:411)
==10686==    by 0x4E98FEA: vfprintf (vfprintf.c:1643)
==10686==    by 0x4EC490F: vsnprintf (vsnprintf.c:114)
==10686==    by 0x108A3E: strdup_printf (tst_free_basic.c:22)
==10686==    by 0x108B09: w_strdup_printf (tst_free_basic.c:34)
==10686==    by 0x108B9A: main (tst_free_basic.c:46)
==10686==  Address 0x522d042 is 2 bytes inside a block of size 17 free'd
==10686==    at 0x4C30D3B: free (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==10686==    by 0x108B7D: main (tst_free_basic.c:44)
==10686==  Block was alloc'd at
==10686==    at 0x4C2FB0F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==10686==    by 0x1089FB: strdup_printf (tst_free_basic.c:17)
==10686==    by 0x108B09: w_strdup_printf (tst_free_basic.c:34)
==10686==    by 0x108B55: main (tst_free_basic.c:42)
==10686==
==10686== Invalid read of size 1
==10686==    at 0x4ECA487: _IO_default_xsputn (genops.c:417)
==10686==    by 0x4E98FEA: vfprintf (vfprintf.c:1643)
==10686==    by 0x4EC490F: vsnprintf (vsnprintf.c:114)
==10686==    by 0x108A3E: strdup_printf (tst_free_basic.c:22)
==10686==    by 0x108B09: w_strdup_printf (tst_free_basic.c:34)
==10686==    by 0x108B9A: main (tst_free_basic.c:46)
==10686==  Address 0x522d048 is 8 bytes inside a block of size 17 free'd
==10686==    at 0x4C30D3B: free (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==10686==    by 0x108B7D: main (tst_free_basic.c:44)
==10686==  Block was alloc'd at
==10686==    at 0x4C2FB0F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==10686==    by 0x1089FB: strdup_printf (tst_free_basic.c:17)
==10686==    by 0x108B09: w_strdup_printf (tst_free_basic.c:34)
==10686==    by 0x108B55: main (tst_free_basic.c:42)
==10686==
b 0x522d4e0
==10686==
==10686== HEAP SUMMARY:
==10686==     in use at exit: 0 bytes in 0 blocks
==10686==   total heap usage: 3 allocs, 3 frees, 1,058 bytes allocated
==10686==
==10686== All heap blocks were freed -- no leaks are possible
==10686==
==10686== For counts of detected and suppressed errors, rerun with: -v
==10686== ERROR SUMMARY: 33 errors from 5 contexts (suppressed: 0 from 0)