使用getchar()和-o3的奇怪行为

我有这两个功能

    void set_dram_channel_width(int channel_width){
      printf("one\n");
          getchar();
    }


    void set_dram_transaction_granularity(int cacheline_size){
      printf("two\n");
          getchar();
    }
    //output:
    one
    f //my keyboard input
    two
    one
    f  //keyboard input
    two
    one
    f  //keyboard input
    //No more calls

然后我将函数更改为:

    void set_dram_channel_width(int channel_width){
      printf("one\n");
    }


    void set_dram_transaction_granularity(int cacheline_size){
      printf("two\n");
      getchar();
    }
    //output
    one
    two 
    f //keyboard input
    //No more calls 

这两个函数都是由外部代码调用的,两个程序的代码是相同的,只需更改getChar()就可以得到这两个不同的输出。这是可能的,还是我的代码中有问题?

谢谢

这是我从gdb获得的输出**

对于第一个代码

(gdb) break mem-dram.c:374
Breakpoint 1 at 0x71c810: file build/ALPHA_FS/mem/dramsim/mem-dram.c, line 374.
(gdb) break mem-dram.c:381
Breakpoint 2 at 0x71c7b0: file build/ALPHA_FS/mem/dramsim/mem-dram.c, line 381.
(gdb) run -d ./tmp/MyBench2/ 
one
f
[Switching to Thread 47368811512112 (LWP 17507)]

Breakpoint 1, set_dram_channel_width (channel_width=64)
(gdb) c
Continuing.
two
one
f

Breakpoint 2, set_dram_transaction_granularity (cacheline_size=64)
(gdb) c
Continuing.

Breakpoint 1, set_dram_channel_width (channel_width=8)
374     void set_dram_channel_width(int channel_width){
(gdb) c
Continuing.
two
one
f

对于第二个代码

(gdb) break mem-dram.c:374
Breakpoint 1 at 0x71c7b6: file build/ALPHA_FS/mem/dramsim/mem-dram.c, line 374.
(gdb) break mem-dram.c:380
Breakpoint 2 at 0x71c7f0: file build/ALPHA_FS/mem/dramsim/mem-dram.c, line 380.
(gdb) run
one
two
f
[Switching to Thread 46985688772912 (LWP 17801)]

Breakpoint 1, set_dram_channel_width (channel_width=64)
(gdb) c
Continuing.

Breakpoint 2, set_dram_transaction_granularity (cacheline_size=64)
(gdb) c
Continuing.

Breakpoint 1, set_dram_channel_width (channel_width=8)
(gdb) c
Continuing.