https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95044
Bug ID: 95044
Summary: -Wreturn-local-addr false alarm in GCC 10.1.0
(regression)
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: eggert at cs dot ucla.edu
Target Milestone: ---
Created attachment 48501
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=48501&action=edit
Illustrate the -Wreturn-local-addr bug.
I ran into this problem when compiling GNU Emacs master with GCC 10.1.0 x86-64,
which I built from source on RHEL 7.7.
Compile the attached program u.c with:
gcc -S -Wreturn-local-addr -O2 u.c
The output is:
u.c: In function 'careadlinkat':
cc1: warning: function may return address of local variable
[-Wreturn-local-add\
r]
u.c:7:8: note: declared here
7 | char stack_buf[1024];
| ^~~~~~~~~
It's obviously impossible for the function to return that address. This false
alarm is not generated by GCC 9.3.0, so this is a regression.
There are really two bugs here:
1. GCC is ignoring the '#pragma GCC diagnostic ignored "-Wreturn-local-addr"'
and is outputting the diagnostic anyway.
2. GCC should not issue a diagnostic even if the pragma is absent, as it's
obviously impossible for the function to return the address of stack_buf.
Both bugs are new to GCC 10.1.0; they do not occur with GCC 9.3.0.
