Thank you for a reply. I read spec on http://www.open-std.org/jtc1/sc22/WG14/www/docs/n1256.pdf then I'm confusing. This spec describes Initialization:
> 6.7.8 Initialization, p127 > > 19 The initialization shall occur in initializer list order, each initializer > provided for a > particular subobject overriding any previously listed initializer for the > same subobject;132) > all subobjects that are not initialized explicitly shall be initialized > implicitly the same as > objects that have static storage duration. What is "be initialized implicitly the same as objects that have static storage duration" mean? 2019年4月2日(火) 9:27 Jeremy O'Brien <neut...@fastmail.com>: > > On Mon, Apr 1, 2019, at 11:33, Kyohei Kadota wrote: > > Hi, 9fans. I use 9legacy. > > > > About below program, I expected that flags field will initialize to > > zero but the value of flags was a garbage, ex, "f8f7". > > Is this expected? > > > > ``` > > #include <stdio.h> > > > > struct option { > > int n; > > char *s; > > int flags; > > }; > > > > int > > main(void) > > { > > struct option opt = {1, "test"}; > > printf("%d %s %x\n", opt.n, opt.s, opt.flags); > > return 0; > > } > > ``` > > > > > > According to C99: "If an object that has automatic storage duration is not > initialized explicitly, its value is indeterminate." > > Stack variable == automatic storage duration. This appears to be correct > behavior to me. >