https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103531
Bug ID: 103531
Summary: Prpose compiler warning when ceil functions used on
integral value
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: eyalroz1 at gmx dot com
Target Milestone: ---
The ceil functions (ceil() and ceilf() in C) take floating-point arguments:
double or float.
If the programmer passes an integer value to one of these functions, it'll get
converted to float/double, and the function will be idempotent. It is thus
typically useless to do so, but also harmless in itself.
But this is _not_ harmless when the programmer assumes they are running ceil()
on what they believe is a floating-point value, but actually isn't. A "typical"
example:
forgot_whether_this_type_is_integral_t x = get_x();
int covers_half = ceil(x / 2);
If x is a floating-point value, this codes will act as expected; but if it's
integral, it will actually place the _floor_ of x / 2.0 in covers_half.
I propose, therefore, that invoking ceil()/ceilf() on an integral value trigger
a warning. Alternatively, that some more complicated conditions trigger the
warning, e.g. invoking ceil() on the result of an integer division or integer
multiplication.
