17:51 scratch $ ./shunting 
*** Error in `./shunting': munmap_chunk(): invalid pointer: 0xb7655f20 ***
======= Backtrace: =========
/usr/lib/libc.so.6(+0x67d2a)[0xb741dd2a]
/usr/lib/libc.so.6(+0x6e9c7)[0xb74249c7]
/usr/lib/libc.so.6(+0x6f051)[0xb7425051]
/usr/lib/libstdc++.so.6(_ZdlPv+0x18)[0xb76534b8]
/usr/lib/libstdc++.so.6(_ZNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEED1Ev
+0x25)[0xb76f38b5]                                                              
./shunting[0x804b52f]
./shunting[0x804b447]
./shunting[0x804b087]
./shunting[0x804adc5]
./shunting[0x804a7fa]
./shunting[0x804a40b]
./shunting[0x804a1af]
./shunting[0x8049fd6]
./shunting[0x80499fc]
/usr/lib/libc.so.6(__libc_start_main+0xf6)[0xb73ce196]
./shunting[0x80493a1]
======= Memory map: ========
08048000-0804e000 r-xp 00000000 08:01 4195078    /home/clairec/scratch/shunting
0804e000-0804f000 r--p 00005000 08:01 4195078    /home/clairec/scratch/shunting
0804f000-08050000 rw-p 00006000 08:01 4195078    /home/clairec/scratch/shunting
09915000-0993a000 rw-p 00000000 00:00 0          [heap]
b73b4000-b73b6000 rw-p 00000000 00:00 0 
b73b6000-b7568000 r-xp 00000000 08:01 12850314   /usr/lib/libc-2.24.so
b7568000-b7569000 ---p 001b2000 08:01 12850314   /usr/lib/libc-2.24.so
b7569000-b756b000 r--p 001b2000 08:01 12850314   /usr/lib/libc-2.24.so
b756b000-b756c000 rw-p 001b4000 08:01 12850314   /usr/lib/libc-2.24.so
b756c000-b756f000 rw-p 00000000 00:00 0 
b756f000-b758b000 r-xp 00000000 08:01 12847372   /usr/lib/libgcc_s.so.1
b758b000-b758c000 r--p 0001b000 08:01 12847372   /usr/lib/libgcc_s.so.1
b758c000-b758d000 rw-p 0001c000 08:01 12847372   /usr/lib/libgcc_s.so.1
b758d000-b75e0000 r-xp 00000000 08:01 12850439   /usr/lib/libm-2.24.so
b75e0000-b75e1000 ---p 00053000 08:01 12850439   /usr/lib/libm-2.24.so
b75e1000-b75e2000 r--p 00053000 08:01 12850439   /usr/lib/libm-2.24.so
b75e2000-b75e3000 rw-p 00054000 08:01 12850439   /usr/lib/libm-2.24.so
b75e3000-b7759000 r-xp 00000000 08:01 12848671   /usr/lib/libstdc++.so.6.0.22
b7759000-b775f000 r--p 00175000 08:01 12848671   /usr/lib/libstdc++.so.6.0.22
b775f000-b7760000 rw-p 0017b000 08:01 12848671   /usr/lib/libstdc++.so.6.0.22
b7760000-b7763000 rw-p 00000000 00:00 0 
b778b000-b778e000 rw-p 00000000 00:00 0 
b778e000-b7790000 r--p 00000000 00:00 0          [vvar]
b7790000-b7791000 r-xp 00000000 00:00 0          [vdso]
b7791000-b77b3000 r-xp 00000000 08:01 12850279   /usr/lib/ld-2.24.so
b77b3000-b77b4000 r--p 00021000 08:01 12850279   /usr/lib/ld-2.24.so
b77b4000-b77b5000 rw-p 00022000 08:01 12850279   /usr/lib/ld-2.24.so
bf8b0000-bf8d1000 rw-p 00000000 00:00 0          [stack]
Abandon (core dumped)

 17:52 scratch $