PR c/39614
	PR c/39673
	* c-common.h (C_MAYBE_CONST_EXPR_PRE, C_MAYBE_CONST_EXPR_EXPR,
	C_MAYBE_CONST_EXPR_INT_OPERANDS, C_MAYBE_CONST_EXPR_NON_CONST,
	EXPR_INT_CONST_OPERANDS): Remove duplicate definitions.
	* c-convert.c (convert): Do not call fold on results of conversion
	functions when the result is a C_MAYBE_CONST_EXPR.
	* c-parser.c (c_parser_postfix_expression): Do not fold condition
	of __builtin_choose_expr.
	* c-typeck.c (remove_c_maybe_const_expr): New.
	(build_unary_op, build_conditional_expr, build_compound_expr,
	build_binary_op, c_objc_common_truthvalue_conversion): Call
	remove_c_maybe_const_expr on any input C_MAYBE_CONST_EXPR with
	integer operands.

testsuite:
	* gcc.c-torture/compile/pr39614-1.c,
	gcc.c-torture/compile/pr39614-2.c,
	gcc.c-torture/compile/pr39614-3.c,
	gcc.c-torture/compile/pr39614-4.c,
	gcc.c-torture/compile/pr39614-5.c,
	gcc.c-torture/compile/pr39673-1.c,
	gcc.c-torture/compile/pr39673-2.c: New tests.
	* gcc.dg/gnu89-const-expr-2.c, gcc.dg/gnu99-const-expr-2.c: Test
	more cases.
	* gcc.dg/overflow-warn-1.c, gcc.dg/overflow-warn-2.c,
	gcc.dg/overflow-warn-3.c, gcc.dg/overflow-warn-4.c: Update
	expected errors.

From-SVN: r145737