Hi, Richard, Thanks a lot for your comments.
> On Dec 21, 2022, at 2:12 AM, Richard Biener <rguent...@suse.de> wrote: > > On Tue, 20 Dec 2022, Qing Zhao wrote: > >> Hi, >> >> This is the patch for mentioning -fstrict-flex-arrays and -Warray-bounds=2 >> changes in gcc-13/changes.html. >> >> Let me know if you have any comment or suggestions. > > Some copy editing below > >> Thanks. >> >> Qing. >> >> ======================================= >> From c022076169b4f1990b91f7daf4cc52c6c5535228 Mon Sep 17 00:00:00 2001 >> From: Qing Zhao <qing.z...@oracle.com> >> Date: Tue, 20 Dec 2022 16:13:04 +0000 >> Subject: [PATCH] gcc-13/changes: Mention -fstrict-flex-arrays and its impact. >> >> --- >> htdocs/gcc-13/changes.html | 15 +++++++++++++++ >> 1 file changed, 15 insertions(+) >> >> diff --git a/htdocs/gcc-13/changes.html b/htdocs/gcc-13/changes.html >> index 689178f9..47b3d40f 100644 >> --- a/htdocs/gcc-13/changes.html >> +++ b/htdocs/gcc-13/changes.html >> @@ -39,6 +39,10 @@ a work-in-progress.</p> >> <li>Legacy debug info compression option <code>-gz=zlib-gnu</code> was >> removed >> and the option is ignored right now.</li> >> <li>New debug info compression option value <code>-gz=zstd</code> has >> been added.</li> >> + <li><code>-Warray-bounds=2</code> will no longer issue warnings for out >> of bounds >> + accesses to trailing struct members of one-element array type >> anymore. Please >> + add <code>-fstrict-flex-arrays=level</code> to control how the >> compiler treat >> + trailing arrays of structures as flexible array members. </li> > > "Instead it diagnoses accesses to trailing arrays according to > <code>-fstrict-flex-arrays</code>." Okay. > >> </ul> >> >> >> @@ -409,6 +413,17 @@ a work-in-progress.</p> >> <h2>Other significant improvements</h2> >> >> <!-- <h3 id="uninitialized">Eliminating uninitialized variables</h3> --> >> +<h3 id="flexible array">Treating trailing arrays as flexible array >> members</h3> >> + >> +<ul> >> + <li>GCC can now control when to treat the trailing array of a structure as >> a >> + flexible array member for the purpose of accessing the elements of such >> + an array. By default, all trailing arrays of structures are treated as > > all trailing arrays in aggregates are treated Okay. > >> + flexible array members. Use the new command-line option >> + <code>-fstrict-flex-array=level</code> to control how GCC treats the >> trailing >> + array of a structure as a flexible array member at different levels. > > <code>-fstrict-flex-arrays</code> to control which trailing array > members are streated as flexible arrays. Okay. > > I've also just now noticed that there's now a flag_strict_flex_arrays > check in the middle-end (in array bound diagnostics) but this option > isn't streamed or handled with LTO. I think you want to replace that > with the appropriate DECL_NOT_FLEXARRAY check. We need to know the level value of the strict_flex_arrays on the struct field to issue proper warnings at different levels. DECL_NOT_FLEXARRAY does not include such info. So, what should I do? Streaming the flag_strict_flex_arrays with LTO? > We might also want > to see how inlining accesses from TUs with different -fstrict-flex-arrays > setting behaves when accessing the same structure (and whether we might > want to issue an ODR style diagnostic there). Yes, good point, I will check on this part. BTW, a stupid question: what does ODR mean? thanks. Qing > > Thanks, > Richard.
