digitalmars.D.bugs - [Issue 3925] New: Missed escaping reference of a local variable
- d-bugmail puremagic.com (37/37) Mar 10 2010 http://d.puremagic.com/issues/show_bug.cgi?id=3925
- d-bugmail puremagic.com (17/18) Mar 10 2010 http://d.puremagic.com/issues/show_bug.cgi?id=3925
- d-bugmail puremagic.com (17/35) Mar 10 2010 http://d.puremagic.com/issues/show_bug.cgi?id=3925
- d-bugmail puremagic.com (21/28) Mar 10 2010 http://d.puremagic.com/issues/show_bug.cgi?id=3925
- d-bugmail puremagic.com (12/12) Oct 22 2010 http://d.puremagic.com/issues/show_bug.cgi?id=3925
- d-bugmail puremagic.com (17/17) Oct 25 2010 http://d.puremagic.com/issues/show_bug.cgi?id=3925
- d-bugmail puremagic.com (7/21) Oct 25 2010 http://d.puremagic.com/issues/show_bug.cgi?id=3925
- d-bugmail puremagic.com (17/17) Jun 29 2011 http://d.puremagic.com/issues/show_bug.cgi?id=3925
http://d.puremagic.com/issues/show_bug.cgi?id=3925 Summary: Missed escaping reference of a local variable Product: D Version: 2.041 Platform: x86 OS/Version: Windows Status: NEW Keywords: diagnostic Severity: normal Priority: P2 Component: DMD AssignedTo: nobody puremagic.com ReportedBy: bearophile_hugs eml.cc This is a wrong program, and the compiler shows the right error messages, of x and y escaping: ref int foo(int x) { return x; } int* baz() { int y; return &y; } void main() {} ------------------- But in the following case the compiler doesn't show an error: ref int foo(ref int x) { return x; } ref int bar() { int x; return foo(x); // escaping reference of x } void main() {} -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Mar 10 2010
http://d.puremagic.com/issues/show_bug.cgi?id=3925 This was the original code by Michel Fortin: safe ref int foo(ref int a) { return a; } safe ref int bar() { int a; return foo(a); } Norbert Nemec comments:I would say the possibility of a bug makes this code unsafe by definition. Ref returns must be considered unsafe by default, unless the compiler can know for sure that the object will exist beyond the lifetime of the function.<So I think Norbert Nemec idea is: while the normal compiler error messages assume correctness and need a demonstration of unsafety to be shown, safe can do the opposite assuming unsafety and requiring a demonstration of safety. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Mar 10 2010
http://d.puremagic.com/issues/show_bug.cgi?id=3925 Don <clugdbug yahoo.com.au> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |clugdbug yahoo.com.auThis was the original code by Michel Fortin: safe ref int foo(ref int a) { return a; } safe ref int bar() { int a; return foo(a); } Norbert Nemec comments:I've just been dealing with ref returns in my recent CTFE patch. But I don't think it's very complicated. As far as I can tell, ref returns are only a problem if a local variable is passed as a ref parameter, or if it is a member function of a local struct. If either of those is true, it should be considered to potentially be a return of a local variable. I don't think there's any problem with foo, but bar should generate an error. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------I would say the possibility of a bug makes this code unsafe by definition. Ref returns must be considered unsafe by default, unless the compiler can know for sure that the object will exist beyond the lifetime of the function.<So I think Norbert Nemec idea is: while the normal compiler error messages assume correctness and need a demonstration of unsafety to be shown, safe can do the opposite assuming unsafety and requiring a demonstration of safety.
Mar 10 2010
http://d.puremagic.com/issues/show_bug.cgi?id=3925 Michel Fortin <michel.fortin michelf.com> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |michel.fortin michelf.com 15:04:05 EST ---I've just been dealing with ref returns in my recent CTFE patch. But I don't think it's very complicated. As far as I can tell, ref returns are only a problem if a local variable is passed as a ref parameter, or if it is a member function of a local struct. If either of those is true, it should be considered to potentially be a return of a local variable. I don't think there's any problem with foo, but bar should generate an error.This seems fair. There is a similar problem with delegates: safe void delegate() foo(ref int a) { return { writeln(a); }; } safe void delegate() bar() { int a; return foo(a); // leaking reference to a beyound bar's scope } It could be solved in the same way. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Mar 10 2010
http://d.puremagic.com/issues/show_bug.cgi?id=3925 Here DMD 2.049 doesn't find the error, but it should: int* foo() { int x; int* p = &x; return p; } void main() {} -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Oct 22 2010
http://d.puremagic.com/issues/show_bug.cgi?id=3925 13:59:45 PDT --- --- class A{} A foo(A a) { return a; } A bar() { scope A a=new A(); return foo(a); } --- -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Oct 25 2010
http://d.puremagic.com/issues/show_bug.cgi?id=3925--- class A{} A foo(A a) { return a; } A bar() { scope A a=new A(); return foo(a); } ---The "scope" is deprecated, so I think yours isn't a valid error case, sorry :-( -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Oct 25 2010
http://d.puremagic.com/issues/show_bug.cgi?id=3925 Two more cases of undetected escaping of reference: int* ptr; void foo1() { int local; ptr = &local; } void foo2(int** x) { int i; *x = &i; } void main() {} See also bug 5541 and bug 1313 -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Jun 29 2011