From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=-0.3 required=5.0 tests=BAYES_00, REPLYTO_WITHOUT_TO_CC autolearn=no autolearn_force=no version=3.4.4 X-Google-Thread: 103376,25ab365b646cef74 X-Google-Attributes: gid103376,domainid0,public,usenet X-Google-Language: ENGLISH,ASCII-7-bit Path: g2news1.google.com!news1.google.com!news.glorb.com!wn13feed!worldnet.att.net!bgtnsc04-news.ops.worldnet.att.net.POSTED!53ab2750!not-for-mail Newsgroups: comp.lang.ada From: anon@anon.org (anon) Subject: Re: GNAT 4.2.3 Ubuntu reports weird compile error wrt Unchecked_Access Reply-To: no to spamers (No@email.given.org) References: <7053ea09-38cd-4e30-9827-a1384bafd190@p31g2000prf.googlegroups.com> X-Newsreader: IBM NewsReader/2 2.0 Message-ID: <37Ppk.5180$Mh5.1917@bgtnsc04-news.ops.worldnet.att.net> Date: Sun, 17 Aug 2008 05:59:27 GMT NNTP-Posting-Host: 12.65.48.183 X-Complaints-To: abuse@worldnet.att.net X-Trace: bgtnsc04-news.ops.worldnet.att.net 1218952767 12.65.48.183 (Sun, 17 Aug 2008 05:59:27 GMT) NNTP-Posting-Date: Sun, 17 Aug 2008 05:59:27 GMT Organization: AT&T Worldnet Xref: g2news1.google.com comp.lang.ada:1637 Date: 2008-08-17T05:59:27+00:00 List-Id: If the GNAT compiler follows the RM on "accessibility" rules. Then it will force you to use the "Unchecked_Access" attribute for any non-local pointer trying to point to local object". Solution: If possible move the object to be access to a package global variable (non-local), then you can use Access attribute. Note: RM 13.10 (1) => "The attribute Unchecked_Access is used to create access values in an unsafe manner -- the programmer is responsible for preventing 'dangling references.' " In <7053ea09-38cd-4e30-9827-a1384bafd190@p31g2000prf.googlegroups.com>, Jerry writes: >I have a curious report from two members of the development team for >PLplot, a popular plotting package for which I have written bindings >in Ada. The project is mature enough that the team decided to enable >Ada by default when building, so I am concerned about the following e- >mail. > >========== begin e-mail ============ > > > >This latest change to the Ada bindings causes a build error for me >with gnat 4.2.3 on Ubuntu. > >plplot.adb:2751:37: non-local pointer cannot point to local object >The offending line is > PL_Pen_Labels(Index) := Temp_C_String'Unchecked_Access; > > > >This must depend on the version of gnat since I don't see this error >for gnat 4.3.1-2 from Debian testing (and I presume Jerry didn't see >it for his gnat-4.3 version as well). > >========= end e-mail ============== > >I (Jerry) in fact did not see a problem on my OS X 4.3 compiler. > >I could supply more details of the code and might even try to write a >small program but testing on someone else's machine would be a bit >tedious. BUT--this error makes no sense to me--I would expect to (and >_do_) see this error if the line in question is > > PL_Pen_Labels(Index) := Temp_C_String'Access; > >The whole purpose of using Unchecked_Access is to make this error go >away. It this a known problem on 4.2.3 Unbutu? Is it a compiler error? >Why does it work as expected on my 4.3 OS X, on 4.3.1-2 Debian >testing, but not 4.2.3 Ubuntu? > >Jerry