Does while(1){} do the same as while(1); - c

Question

I just want to be sure that this C code:
while(flag==true)
{
}
foo();
does the same as this:
while(flag==true);
foo();

Answer 1

; alone is a null statement in C.
In your case, {} or ; are syntactically needed, but they do the same: nothing
Related: Use of null statement in C

Answer 2

In addition to the other answers: It's the same thing.
But I prefer this:
while (condition)
{
}
foo();
over this:
while (condition);
foo();
because if you forget the semicolon after the while, your code will compile fine but it won't do what you expect:
while(condition) // ; forgotten here
foo();
will actually be equivalent of:
while(condition)
{
foo();
}

Answer 3

Yes, having an empty body of the loop is equivaled to just while(<some condition>);

Answer 4

Yes. A ; following a control structure (e.g., while, for, etc.) that can be followed with a block is treated as if it was followed by an empty block.

Answer 5

Yes, because when put semicolon after while loop statement that indicate empty body and when the condition becomes false then it goes to the immediate next statement after that loop. 

Answer 6

Yes, they are same.
You Can Generate The assembly of the code and see for yourself that they produce the same assembly. (Using gcc filename.c -S -masm=intel -o ouputfilename)
#include<stdio.h>
int foo(void);
int main(){
int flag;
scanf("%d" , &flag);
while(flag==1);
foo();
}
int foo(void){
int x = 2;
return x*x;
}
.LC0:
.ascii "%d\0"
.text
.globl main
.def main; .scl 2; .type 32; .endef
.seh_proc main
main:
push rbp
.seh_pushreg rbp
mov rbp, rsp
.seh_setframe rbp, 0
sub rsp, 48
.seh_stackalloc 48
.seh_endprologue
call __main
lea rax, -4[rbp]
mov rdx, rax
lea rcx, .LC0[rip]
call scanf
nop
.L2:
mov eax, DWORD PTR -4[rbp]
cmp eax, 1
je .L2
call foo
mov eax, 0
add rsp, 48
pop rbp
ret
.seh_endproc
.globl foo
.def foo; .scl 2; .type 32; .endef
.seh_proc foo
foo:
push rbp
.seh_pushreg rbp
mov rbp, rsp
.seh_setframe rbp, 0
sub rsp, 16
.seh_stackalloc 16
.seh_endprologue
mov DWORD PTR -4[rbp], 2
mov eax, DWORD PTR -4[rbp]
imul eax, DWORD PTR -4[rbp]
add rsp, 16
pop rbp
ret
.seh_endproc
.ident "GCC: (x86_64-posix-seh-rev1, Built by MinGW-W64 project) 6.3.0"
.def scanf; .scl 2; .type 32; .endef
And When I Changed while(flag == 1); to while(flag==1){} Assembly Code Generated is :
.LC0:
.ascii "%d\0"
.text
.globl main
.def main; .scl 2; .type 32; .endef
.seh_proc main
main:
push rbp
.seh_pushreg rbp
mov rbp, rsp
.seh_setframe rbp, 0
sub rsp, 48
.seh_stackalloc 48
.seh_endprologue
call __main
lea rax, -4[rbp]
mov rdx, rax
lea rcx, .LC0[rip]
call scanf
nop
.L2:
mov eax, DWORD PTR -4[rbp]
cmp eax, 1
je .L2
call foo
mov eax, 0
add rsp, 48
pop rbp
ret
.seh_endproc
.globl foo
.def foo; .scl 2; .type 32; .endef
.seh_proc foo
foo:
push rbp
.seh_pushreg rbp
mov rbp, rsp
.seh_setframe rbp, 0
sub rsp, 16
.seh_stackalloc 16
.seh_endprologue
mov DWORD PTR -4[rbp], 2
mov eax, DWORD PTR -4[rbp]
imul eax, DWORD PTR -4[rbp]
add rsp, 16
pop rbp
ret
.seh_endproc
.ident "GCC: (x86_64-posix-seh-rev1, Built by MinGW-W64 project) 6.3.0"
.def scanf; .scl 2; .type 32; .endef
You can see that the relevant portion is same in both cases.
//Below Portion is same in both cases.
.L2:
mov eax, DWORD PTR -4[rbp]
cmp eax, 1
je .L2
call foo
mov eax, 0
add rsp, 48
pop rbp
ret
.seh_endproc
.globl foo
.def foo; .scl 2; .type 32; .endef
.seh_proc foo