[Bug c/100702] Strict overflow warning regression in gcc 8 onwards

["david at westcontrol dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100702

--- Comment #2 from David Brown <david at westcontrol dot com> ---
Runtime diagnostics can be very useful - but they are a different kind of
warning.  In particular, they only show what errors have occurred during your
testing - they don't show what errors /might/ occur.

There is a general rule that the earlier you find your problems, the cheaper,
faster and easier they are to handle.  Compile-time checks are better than
run-time checks when all else is equal.  Clearly compile-time checks have more
risk of false-positives - that's why it's important that most are optional or
can be disabled by pragmas or particular code constructs.  But when they /can/
be used, they are preferable.

In this particular example, there is no doubt of the undefined behaviour and
the infinite loop.  The compiler knows about them.  It would not be a false
positive to issue a warning in such cases.


Another limitation of runtime diagnostics is their use in embedded systems. 
gcc is heavily used in microcontrollers, where you often do not have much in
the way of a console output, no file system, etc.  Runtime diagnostic
opportunities are far more limited in such cases.


I fully appreciate that compile-time warnings are difficult, especially
avoiding false positives, and if you say that a warning here would be too niche
or too difficult to justify the effort, I am happy to accept that.  But
run-time diagnostics are not a replacement - they are an additional and
complementary tool.  Please do not consider sanitizers as a substitute for
static analysis and compile-time error checking and warnings.