https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65471
Bug ID: 65471
Summary: type interpretation in _Generic
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: jens.gustedt at inria dot fr
This is a bug marker for an underspecification in the C11 standard, that has
been observed in DR#423
http://www.open-std.org/jtc1/sc22/wg14/www/docs/summary.htm#dr_423
gcc and clang went quite opposite ways to resolve that issue, resulting in
severe incompatibility for _Generic expression that use qualifiers or arrays.
The following six lines illustrate the problem
char const* a = _Generic("bla", char*: "blu"); // clang error
char const* b = _Generic("bla", char[4]: "blu"); // gcc error
char const* c = _Generic((int const){ 0 }, int: "blu"); // clang error
char const* d = _Generic((int const){ 0 }, int const: "blu"); // gcc error
char const* e = _Generic(+(int const){ 0 }, int: "blu"); // both ok
char const* f = _Generic(+(int const){ 0 }, int const: "blu"); // both error
the last two lines, where gcc and clang agree, points to the nature of the
problem: gcc treats all such expressions as rvalues, clang as lvalues.
