[Bug c/57612] add builtin to assert that expression does not have side effects
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57612 David L. changed: What|Removed |Added CC||equinox-gccbugs at diac24 dot net --- Comment #5 from David L. --- I would like to "third" this request. In my head I was thinking of a "__builtin_warn_side_effects(x[, "extra warning text"])" that returns the value of x, but if the parameter does not actually get evaluated a "__builtin_pure_p(x)" test returning 0/1 works too I guess.
[Bug c/57612] add builtin to assert that expression does not have side effects
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57612 --- Comment #4 from Tom Tromey --- (In reply to H. Peter Anvin from comment #2) > I would like to second this request, however, I would like to request that > it issues a warning rather than an error. It can always be promoted to an > error via -Werror= or the equivalent pragma. What's the use case for this? It seems simpler to just not use this macro when you don't want the effect. (In reply to felix from comment #3) > Overlaps bug 6906. Under that ticket, I proposed adding a built-in that > simply returns whether or not a given expression has side effects, simply by > exposing TREE_SIDE_EFFECTS(). This seems the same to me, in that __builtin_assert_no_side_effects could, I think, just be a static_assert using your builtin.
[Bug c/57612] add builtin to assert that expression does not have side effects
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57612
felix changed:
What|Removed |Added
CC||felix.von.s at posteo dot de
--- Comment #3 from felix ---
Overlaps bug 6906. Under that ticket, I proposed adding a built-in that simply
returns whether or not a given expression has side effects, simply by exposing
TREE_SIDE_EFFECTS(). This more general built-in could also (partially) address
bug 79469, by allowing to define __builtin_assume as
#define __builtin_assume(cond) do { \
if (__builtin_pure_p(cond)) \
if (!(cond)) \
__builtin_unreachable(); \
} while (0)
Partially, because e.g. if A has side effects, then with the definition above
__builtin_assume(A && B) would consider the whole condition to have side
effects as well, and therefore disregard it, even if B could potentially be
mined for optimisation opportunities.
[Bug c/57612] add builtin to assert that expression does not have side effects
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57612 H. Peter Anvin changed: What|Removed |Added CC||hpa at zytor dot com --- Comment #2 from H. Peter Anvin --- I would like to second this request, however, I would like to request that it issues a warning rather than an error. It can always be promoted to an error via -Werror= or the equivalent pragma.
[Bug c/57612] add builtin to assert that expression does not have side effects
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57612 --- Comment #1 from Tom Tromey --- You can see the thread here: http://patchwork.ozlabs.org/patch/343858/ My proposed patch didn't handle C++, which seems like something it probably should do.
