1316978 - Tons of warning spam from passing nullptr to NSCAP_LOG_ASSIGNMENT

Status: RESOLVED FIXED

(Core :: XPCOM, defect)

Description

[Boris Zbarsky [:bzbarsky]]

The changes in bug 1316432 started passing nullptr to NSCAP_LOG_ASSIGNMENT.  Now I get tons of compiler warnings like this when building:

 0:15.28 Warning: -Wnull-conversion in /Users/bzbarsky/mozilla/inbound/obj-firefox/dist/include/nsCOMPtr.h: implicit conversion of nullptr constant to 'bool'
 0:15.28 ../../dist/include/nsCOMPtr.h:518:32: warning: implicit conversion of nullptr constant to 'bool' [-Wnull-conversion]
 0:15.28     NSCAP_LOG_ASSIGNMENT(this, nullptr);
 0:15.31                                ^~~~~~~
 0:15.31                                false
 0:15.31 ../../dist/include/nsISupportsImpl.h:135:7: note: expanded from macro 'NSCAP_LOG_ASSIGNMENT'
 0:15.31   if (_p)               

etc (listing the template expansion, the include chain, and so forth).  Adds up to thousands of lines per unified cpp file....

Comment 1

[Gerald Squelart (he/him) (not at Mozilla since 2022-09-15)]

Thank you for letting me know.

Comment 2

[Gerald Squelart (he/him) (not at Mozilla since 2022-09-15)]

Attachment: Bug 1316978 - Suppress nullptr-to-bool cast warning -

Review commit: https://reviewboard.mozilla.org/r/92452/diff/#index_header
See other reviews: https://reviewboard.mozilla.org/r/92452/

Comment 3

[Nathan Froyd [:froydnj]]

Comment on attachment 8809972 [details]
Bug 1316978 - Suppress nullptr-to-bool cast warning -

https://reviewboard.mozilla.org/r/92452/#review92510

r=me with the below fixed.

::: xpcom/glue/nsISupportsImpl.h:137
(Diff revision 1)
>   * These logging functions require dynamic_cast<void*>, so they don't
> - * do anything useful if we don't have dynamic_cast<void*>. */
> + * do anything useful if we don't have dynamic_cast<void*>.
> + * Note: The explicit comparison to nullptr is needed to avoid warnings
> + *       when _p is a nullptr itself. */
>  #define NSCAP_LOG_ASSIGNMENT(_c, _p)                                \
> -  if (_p)                                                           \
> +  if (_p == nullptr)                                                \

Surely this is supposed to be `_p != nullptr`?

Comment 4

[Gerald Squelart (he/him) (not at Mozilla since 2022-09-15)]

Comment on attachment 8809972 [details]
Bug 1316978 - Suppress nullptr-to-bool cast warning -

Review request updated; see interdiff: https://reviewboard.mozilla.org/r/92452/diff/1-2/

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/99603b2447b8
Suppress nullptr-to-bool cast warning - r=froydnj

Comment 6

[Carsten Book [:Tomcat]]

https://hg.mozilla.org/mozilla-central/rev/99603b2447b8