Can not use C99 function names as variable names in C89

Bugzilla Link	15150
Version	unspecified
OS	All
Reporter	LLVM Bugzilla Contributor
CC	@gribozavr

Extended Description

The following code doesn't compile in clang, but does in gcc:

int logf = 5;
int main() {
        return logf;
}

# gcc test.c -o test -std=c89
# ./test; echo $?
5
# clang test.c -o test -std=c89
test.c:1:5: error: redefinition of 'logf' as different kind of symbol
int logf = 5;
    ^
test.c:1:5: note: previous definition is here
test.c:4:16: warning: incompatible pointer to integer conversion returning 'float (float)' from a function with result type 'int' [-Wint-conversion]
        return logf;
               ^~~~
1 warning and 1 error generated.