On 9/23/05, Marcin Kalicinski <kalita@poczta.onet.pl> wrote:
Hi Everybody,
I see there are mixed opinions on use of __assume in BOOST_ASSERT. The chief concern is there are people using BOOST_ASSERT in "uncommon" (but still valid) ways, such as:
- to show dialog box, but only in debug mode - using assert handler to throw during unit testing - possibly more
These types of usage would be prohibited if we introduced __assume into BOOST_ASSERT, so basically this is a no-no from stability point of view (nobody wants his code broken). Btw. the second way can be dealt with with disabling __assume if assertion handler is defined.
On the other hand some people (including me) consider __assume to be nice, helping optimization and suppressing annoying warnings. I see 3 options:
1. BOOST_ASSUME ===============================================
Put __assume in BOOST_ASSUME and leave BOOST_ASSERT unmodified.
Pros: - does not disturb existing code in any way
Cons: - no existing code uses it, i.e. all existing libraries would have to be modified to take advantage of it; this will probably never happen so most of the code will not benefit - obscure: most of the people would be confused about it when seeing it for the first time
I prefer this way. I do not think it's a hard concept to understand and it would be fairly trivial for authors to change their BOOST_ASSERTs to use it where appropriate. Using a define to change BOOST_ASSERT limits you to either having it on or off through the whole file, but BOOST_ASSUME would let you pick and choose which is best for the situation.
2. BOOST_ASSERT + define to enable assume (default: on) ===============================================
Pros: - does enable assume on all the boost code, some user programs get somewhat smaller and faster without any intervention from the programmer
Cons: - breaks user code which uses BOOST_ASSERT in "uncommon" way. Would require a change in docs that executing BOOST_ASSERT(false) is undefined behavior (i.e. different than std::assert)
BOOST_ASSERT + define to enable assume (default: off) ===============================================
Pros: - does enable assume on all the boost code, some user programs get smaller and faster with a simple -D"BOOST_ASSERT_USE_ASSUME" on command line.
Cons: - only small number of users will know about that #define, so probably most of the code will not benefit.
What do you think?
Marcin
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