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Fix remaining clang warnings for fallthrough switch cases (in debug build). (#10314)

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https://github.com/Z3Prover/z3/pull/10284 changed the UNREACHABLE macro
in debug.h to use __builtin_unreachable() to indicate to the compiler
that the
code leading it should be considered unreachable.

In https://github.com/Z3Prover/z3/pull/10295 Copilot figured out that
this was wrong: the unreachable macro makes calls, which shouldn't be
elided, and whose arguments should be evaluated. It partially fixed the
problem by declaring invoke_exit_action to be `[[noreturn]]`. This
eliminated warnings in non-debug builds, but when Z3_DEBUG is enabled,
`UNREACHABLE` ends with an invocation of `INVOKE_DEBUGER()`. This can
call `invoke_debugger()`, which *can* actually return (so it can't be
given the `[[noreturn]]` attribute. So we still get warnings in debug
builds.

This PR fixes those, creating a Z3_unreachable_case macro, which is just
a combination of `UNREACHABLE()` and `Z3_fallthrough`. It uses that in
the places that give warnings.

It seemed better to me to still have these cases have a single macro,
rather than `UNREACHABLE` followed by an explicit `Z3_fallthrough`; this
seemed to me like it would confuse people -- "how can you fall through
if this code is unreachable?" But I'm open to alternative suggestions!
This commit is contained in:
davedets 2026-07-30 19:24:46 -07:00 • committed by GitHub
parent 141e99ffe7
commit c49eb07c3e
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6 changed files with 11 additions and 5 deletions
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2
src/ast/rewriter/array_rewriter.cpp
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@ -328,7 +328,7 @@ br_status array_rewriter::mk_select_core(unsigned num_args, expr * const * args,
SASSERT(to_app(args[0])->get_num_args() == num_args+1);
switch (compare_args(num_args - 1, args+1, to_app(args[0])->get_args()+1)) {
case l_true:
UNREACHABLE();
Z3_unreachable_case();
case l_false: {
expr* arg0 = to_app(args[0])->get_arg(0);
while (m_util.is_store(arg0) && compare_args(num_args-1, args + 1, to_app(arg0)->get_args() + 1) == l_false) {