我的C程序默认是多线程还是stdout对我的打印语句重新排序？

Question

I am running into a weird issue. I wrote a simple c program (two source files, relevant sections shown below). When I run the program (ac has the main function), I get the output (since the number of times I am calling "process" is high, I am printing the last few print outs from the output to the screen):

key: 'Q'
key: 'A'
1
key: 'A'
key: 'A'
1
key: 'A'
key: 'A'
1
key: 'A'
key: 'A'
key: 'C'
Segmentation fault (core dumped)

ac

void process(int* hash, char* input, int number_of_ac) {
int value, i = 0;
for(; i < number_of_ac; i++) {
value = get_value(hash, input[i]);
printf("1\\n");
increment_value(hash, input[i]);
}
}

bc

int get_value(int* hash, char key) {
printf("key: '%c'\\n", key);
return hash[get_index(key)];
}

void increment_value(int* hash, char key) {
int value = get_value(hash, key);
hash[get_index(key)] = ++value;
}

My question specifically is (the ultimate goal is for me to try to debug why I am getting a segmentation fault on a high number of "process" calls and not on a smaller number of calls), shouldn't I see a print out like this:

key: 'Q'
1
key: 'A'
1
key: 'A'
1
key: 'A'
etc.

Why do I see a print of two letters before I see the 1 again? Is this a buffer reordering issue of my statements being printed to the screen? Or, is it somehow my c program is multi-threading behind the scene?

By the way, this exact same program runs on my laptop with a MUCH LARGER set of input:

Linux ubuntu 3.8.0-25-generic #37-Ubuntu SMP Thu Jun 6 20:47:07 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux

But it breaks with the Segmentation Fault above on a much smaller input on another machine:

Linux xyz 2.6.32-279.19.1.el6.cny6.7068.x86_64 #1 SMP Mon Mar 11 08:59:43 CDT 2013 x86_64 x86_64 x86_64 GNU/Linux

Any ideas? I appreciate your assistance!

Answer 1

Look how you call increment value:

void increment_value(int* hash, char key) {
   int value = get_value(hash, key); // calling get_value
   hash[get_index(key)] = ++value;
}

so you are printing a char here and you call get_value again in process function. That why you are getting multiples prints of chars before '1'