https://bugs.llvm.org/show_bug.cgi?id=46993
Bug ID: 46993
Summary: Warn when an empty while loop could have been a
do-while
Product: clang
Version: 10.0
Hardware: PC
OS: Linux
Status: NEW
Severity: enhancement
Priority: P
Component: -New Bugs
Assignee: unassignedclangb...@nondot.org
Reporter: josephcsi...@gmail.com
CC: htmldevelo...@gmail.com, llvm-bugs@lists.llvm.org,
neeil...@live.com, richard-l...@metafoo.co.uk
Consider this C code:
typedef int sig_atomic_t;
volatile sig_atomic_t signaled;
_Bool getX(int *);
void processX(int);
void f(void)
{
{
int x;
if(getX(&x))
processX(x);
}
while(!signaled);
/* do some other stuff */
}
There's two possibilities for what the author meant for it to do:
1. Do getX (and maybe processX) once (in a block just to minimize the scope of
x), then busy-wait until signaled becomes true, and then do some other stuff.
This is what it actually does.
2. Keep doing getX (and maybe processX) in a loop until signaled becomes true,
and then do some other stuff. This isn't what it actually does, because the
author forgot the "do" keyword.
We currently emit no relevant warnings for this code, even when compiled with
"-Weverything". I propose that when we see "while(condition);", we warn that a
"do" may be missing, and if it's not, that you should use "while(condition){}"
instead (except in cases where it's impossible to just be missing the "do"
keyword, like if the "while" is at the beginning of a block).
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