Question

我正在为NetBSD系统使用英特尔的ICC编译器。我一直在与一个bug斗争，当我从核心转储中观察到来自gdb中两个不同机制的符号地址不同时，我更加惊讶。

当使用＆＃34; info symbol connection_out＆＃34;检查时，变量connection_out似乎具有不同的地址。和p＆amp; connection_out。

它是否看起来像编译器问题，其中优化为CPU寄存器的badf_errcnt被分配了一个内存位置，然后编译器在两者之间混淆了？

我有编译器O2级别优化ON。有问题的变量是一个全局静态int变量。我不认为指针别名在此处起作用，因为正在使用变量的内存位置。

我看到未经剥离的符号文件也同意反汇编代码中的地址。

gdb$ disassemble sigusr1_rt
Dump of assembler code for function sigusr1_rt:
   0x01845000 <+0>:     push   %ebp
   0x01845001 <+1>:     mov    %esp,%ebp
   0x01845003 <+3>:     sub    $0x8,%esp
   0x01845006 <+6>:     movl   $0x16c156a,0x188f05c
   0x01845010 <+16>:    mov    %ebp,%esp
   0x01845012 <+18>:    pop    %ebp
   0x01845013 <+19>:    ret    
   0x01845014 <+20>:    lea    0x0(%esi),%esi
   0x0184501a <+26>:    lea    0x0(%edi),%edi
End of assembler dump.
gdb$ info symbol 0x188f05c
connection_out in section .bss of /sites/eqx/work/swcores/tripunjay/F10ACOREDIR/f10cp_sshd.login-eqx-06.6402/sshd
gdb$ p &connection_out
$10 = (int *) 0x188f048
gdb$ p/d 0x188f05c - 0x188f048
$11 = 20
gdb$ p/x 0x188f05c - 0x188f048 
$12 = 0x14
gdb$ info symbol 0x188f048
badf_errcnt.5450.0.13 in section .bss of /sites/eqx/work/swcores/tripunjay/F10ACOREDIR/f10cp_sshd.login-eqx-06.6402/sshd
gdb$ p &badf_errcnt
No symbol "badf_errcnt" in current context.
gdb$ select-frame 5
gdb$ frame         
Stack level 5, frame at 0xbb4aca20:
 eip = 0x1846007 in wait_until_can_do_something (serverloop.c:404); saved eip 0x1846698
 called by frame at 0xbb4b0af0, caller of frame at 0xbb4ac9d0
 source language c.
 Arglist at 0xbb4aca18, args: readsetp=0xbb4b0ab4, writesetp=0xbb4b0ab8, maxfdp=0x4, nallocp=0xbb4b0abc, max_time_milliseconds=0x0
 Locals at 0xbb4aca18, Previous frame's sp is 0xbb4aca20
 Saved registers:
  ebx at 0xbb4aca00, ebp at 0xbb4aca18, esi at 0xbb4ac9fc, edi at 0xbb4aca04, eip at 0xbb4aca1c
readsetp = 0xbb4b0ab4
writesetp = 0xbb4b0ab8
maxfdp = 0x4
nallocp = 0xbb4b0abc
max_time_milliseconds = 0x0
badf_errcnt = <optimized out>
tv = <optimized out>
tvp = <optimized out>
client_alive_scheduled = 0x0
gdb$ p &badf_errcnt
Can't take address of "badf_errcnt" which isn't an lvalue.


prompt$ nm sshd.unstripped | grep connection_out   
0188f05c b connection_out

Answer 1

这看起来像ICC生成的调试信息或链接器中的可能错误。

特别是，符号表中的connection_out地址似乎与connection_out中.debug_info的地址不符。

要在符号表中查找&connection_out，请执行以下操作：

readelf -Ws /sites/.../f10cp_sshd.login-eqx-06.6402/sshd |
  grep connection_out

并与

的输出进行比较

readelf -wi /sites/.../f10cp_sshd.login-eqx-06.6402/sshd

应该有connection_out的条目，与此类似：

<1><b6>: Abbrev Number: 9 (DW_TAG_variable)
    <b7>   DW_AT_name        : (indirect string, offset: 0x84): connection_out 
    <bb>   DW_AT_decl_file   : 1        
    <bc>   DW_AT_decl_line   : 5        
    <bd>   DW_AT_type        : <0x73>   
    <c1>   DW_AT_external    : 1        
    <c1>   DW_AT_location    : 9 byte block: 3 60 10 60 0 0 0 0 0       (DW_OP_addr: 601060)

如果符号表中的地址与.debug_info（DW_AT_location条目）中的地址不同，则会出现编译器（或链接器）错误。如果它们相同，则会出现GDB错误。

它是GDB错误还是英特尔编译器错误或我的代码？

1 个答案: