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As noted in bug 88642, the C front end fails to give errors or pedwarns for scalar initializers with too many levels of surrounding braces. There is a warning for redundant braces around a scalar initializer within a larger braced initializer (valid for a single such level within a structure, union or array initializer; not valid for more than one such level, or where the outer layer of braces is itself for a scalar, either redundant braces themselves or part of a compound literal), but this never becomes an error even for invalid cases. Check for this case and turn the warning into a permerror when there are more levels of braces than permitted. The existing warning is unchanged for a single (permitted) level of redundant braces around a scalar initializer inside a structure, union or array initializer, and it's also unchanged that no such warning is given for a single (permitted) level of redundant braces around a top-level scalar initializer. Technically this is a C2y issue (these rules on valid initializers moved into Constraints as a result of N3346, accepted in Minneapolis; previously, as a "shall" outside constraints, violating these rules resulted in compile-time undefined behavior without requiring a diagnostic). Hopefully little code is actually relying on not getting an error here. In view of gcc.dg/tree-ssa/ssa-dse-10.c showing that at least some code may be using such over-braced initializers (initializer of pubKeys at line 1167 in that test; I'm not at all sure how that initializer ends up getting interpreted to translate it to something equivalent but properly structured), this is made a permerror rather than a hard error, so -fpermissive (as already used by that test) can be used to disable the error (the default -fpermissive for old standards modes is not a problem given that before C2y this is undefined behavior not a constraint violation). Bootstrapped with no regressions for x86_64-pc-linux-gnu. PR c/88642 gcc/c/ * c-typeck.cc (constructor_braced_scalar): New variable. (struct constructor_stack): Add braced_scalar field. (really_start_incremental_init): Handle constructor_braced_scalar and braced_scalar field. (push_init_level): Handle constructor_braced_scalar and braced_scalar field. Give permerror rather than warning for nested braces around scalar initializer. (pop_init_level): Handle constructor_braced_scalar and braced_scalar field. gcc/testsuite/ * gcc.dg/c2y-init-1.c: New test.
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