https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84293
Bug ID: 84293
Summary: system-header macro expansion location gives
unexpected warning
Product: gcc
Version: 8.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: nathan at gcc dot gnu.org
Target Milestone: ---
Created attachment 43379
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=43379&action=edit
source file
The attached tescase (2 files) gives the following warning:
nathans@devvm2452:104>./xgcc -B./ -nostdinc -isystem . -c pun.c
pun.c: In function 'init':
pun.c:7:3: warning: dereferencing type-punned pointer will break
strict-aliasing rules [-Wstrict-aliasing]
INCREF_BAD (&thing); /* Warning. */
^~~~~~~~~~
The actual dereference is happening in a system header file, so this should be
protected. And indeed that's what happens in the expansion of 'INCREF_OK
(&thing)' The only difference being the BAD one uses a typedef name and the OK
one uses 'struct name'.
In the typedef case we think the cast location is the macro expansion point.
in the struct name case we think it's the name token's location.
If one adds -save-temps the warning goes away. We no longer see the macro
expansions.
