PR tree-optimization/79327 - wrong code at -O2 and -fprintf-return-value
gcc/ChangeLog:
	* gimple-ssa-sprintf.c (tree_digits): Avoid adding the base prefix
	when precision has resulted in leading zeros.
	(format_integer): Adjust the likely counter to assume an unknown
	argument that may be zero is non-zero.

gcc/testsuite/ChangeLog:
	* gcc.dg/tree-ssa/builtin-sprintf-warn-1.c: Adjust.
	* gcc/testsuite/gcc.dg/tree-ssa/builtin-sprintf-warn-13.c: New test.
	* gcc/testsuite/gcc.dg/tree-ssa/pr79327-2.c: Ditto.

From-SVN: r245173