C compiler not noticing errors and correcting code itself

So I am a beginner in C and I have been following a book Primer Plus 6th edition.While I was running my program I noticed something really strange, compiler is not working as it is supposed to, for example

int main(){    one_three();    getchar();    return 0;}void one_three(void){    printf("one\n");    two();    printf("three");}void two(void){    printf("two\n");}

this is my code, there are many errors as no function prototype declarations and not including header files, but some how the output is produced only by giving warnings, i dont think this should happenNOTE I HAVE INTENTIONALLY REMOVED FUNCTION PROTOTYPE DECLARTAIONS AND INCLUDING HEADER FILES

output is :

review1.c: In function 'main':review1.c:2:5: warning: implicit declaration of function 'one_three' [-Wimplicit-function-declaration]    2 |     one_three();      |     ^~~~~~~~~review1.c:3:5: warning: implicit declaration of function 'getchar' [-Wimplicit-function-declaration]    3 |     getchar();      |     ^~~~~~~review1.c:1:1: note: 'getchar' is defined in header '<stdio.h>'; did you forget to '#include <stdio.h>'?+++ |+#include <stdio.h>    1 | int main(){review1.c: At top level:review1.c:7:6: warning: conflicting types for 'one_three'    7 | void one_three(void){      |      ^~~~~~~~~review1.c:2:5: note: previous implicit declaration of 'one_three' was here    2 |     one_three();      |     ^~~~~~~~~review1.c: In function 'one_three':review1.c:8:5: warning: implicit declaration of function 'printf' [-Wimplicit-function-declaration]    8 |     printf("one\n");      |     ^~~~~~review1.c:8:5: warning: incompatible implicit declaration of built-in function 'printf'review1.c:8:5: note: include '<stdio.h>' or provide a declaration of 'printf'review1.c:9:5: warning: implicit declaration of function 'two' [-Wimplicit-function-declaration]    9 |     two();      |     ^~~review1.c: At top level:review1.c:13:6: warning: conflicting types for 'two'   13 | void two(void){      |      ^~~review1.c:9:5: note: previous implicit declaration of 'two' was here    9 |     two();      |     ^~~review1.c: In function 'two':review1.c:14:5: warning: incompatible implicit declaration of built-in function 'printf'   14 |     printf("two\n");      |     ^~~~~~review1.c:14:5: note: include '<stdio.h>' or provide a declaration of 'printf'one twothree

those last three lines "one" two three is the outputPlease help, i am using this compiler

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I expect it to output errors when it has to and not add stuff itself, so that i could learn by my mistakesusing visual studio code with extensions : C/C++ by microsoft, Code runner