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Tested on x86_64 with gcc 4.8.2.

CFLAGS="-march=native -Os"

gcc generates the smartlist_ensure_capacity() function code:

Dump of assembler code for function smartlist_ensure_capacity:
   0x00000000004c2ad1 <+0>:     push   %rbx
   0x00000000004c2ad2 <+1>:     mov    %rdi,%rbx
   0x00000000004c2ad5 <+4>:     cmp    0xc(%rdi),%esi
   0x00000000004c2ad8 <+7>:     jle    0x4c2b00 <smartlist_ensure_capacity+47>
   0x00000000004c2ada <+9>:     cmp    $0x3fffffff,%esi
   0x00000000004c2ae0 <+15>:    jg     0x4c2ae4 <smartlist_ensure_capacity+19>
   0x00000000004c2ae2 <+17>:    jmp    0x4c2ae2 <smartlist_ensure_capacity+17>
   0x00000000004c2ae4 <+19>:    movl   $0x7fffffff,0xc(%rdi)
   0x00000000004c2aeb <+26>:    mov    (%rdi),%rdi
   0x00000000004c2aee <+29>:    movabs $0x3fffffff8,%rsi
   0x00000000004c2af8 <+39>:    callq  0x4ca268 <tor_realloc_>
   0x00000000004c2afd <+44>:    mov    %rax,(%rbx)
   0x00000000004c2b00 <+47>:    pop    %rbx
   0x00000000004c2b01 <+48>:    retq   
End of assembler dump.

We can clearly see that 0x00000000004c2ae2 <+17>: jmp 0x4c2ae2 <smartlist_ensure_capacity+17> is an infinite loop.

If now, we use the size parameter, for instance by doing the following at the beginning of the function:

  sl->trick = size;

Then gcc generates correct code:

Dump of assembler code for function smartlist_ensure_capacity:
   0x00000000004c2ad1 <+0>:     push   %rbx
   0x00000000004c2ad2 <+1>:     mov    %rdi,%rbx
   0x00000000004c2ad5 <+4>:     mov    0xc(%rdi),%eax
   0x00000000004c2ad8 <+7>:     mov    %esi,0x10(%rdi)
   0x00000000004c2adb <+10>:    cmp    %eax,%esi
   0x00000000004c2add <+12>:    jle    0x4c2b0c <smartlist_ensure_capacity+59>
   0x00000000004c2adf <+14>:    cmp    $0x3fffffff,%esi
   0x00000000004c2ae5 <+20>:    jg     0x4c2aef <smartlist_ensure_capacity+30>
   0x00000000004c2ae7 <+22>:    add    %eax,%eax
   0x00000000004c2ae9 <+24>:    cmp    %eax,%esi
   0x00000000004c2aeb <+26>:    jg     0x4c2ae7 <smartlist_ensure_capacity+22>
   0x00000000004c2aed <+28>:    jmp    0x4c2af4 <smartlist_ensure_capacity+35>
   0x00000000004c2aef <+30>:    mov    $0x7fffffff,%eax
   0x00000000004c2af4 <+35>:    mov    (%rbx),%rdi
   0x00000000004c2af7 <+38>:    mov    %eax,0xc(%rbx)
   0x00000000004c2afa <+41>:    cltq   
   0x00000000004c2afc <+43>:    lea    0x0(,%rax,8),%rsi
   0x00000000004c2b04 <+51>:    callq  0x4ca274 <tor_realloc_>
   0x00000000004c2b09 <+56>:    mov    %rax,(%rbx)
   0x00000000004c2b0c <+59>:    pop    %rbx
   0x00000000004c2b0d <+60>:    retq   
End of assembler dump.

Here, no infinite loop anymore.

As of 2013-11-30T23:19:42 EST I'm trying to dig further.

Trac:
Username: zougloub