https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109542
Bug ID: 109542
Summary: bad detection of null dereferance cause ud2a in valid
inline function code
Product: gcc
Version: 11.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: amos.maimon at sap dot com
Target Milestone: ---
Created attachment 54881
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=54881&action=edit
snip code that reproduce the issue that decribe above
There is a bug in the detection of null dereferance - and user code change to
UD2A.
This happened when the function picked to be inline.
How to reproduce:
1. download the attached code snip.
2. compile with the following params:
gcc -Wall -Werror -Wno-packed-not-aligned -Wno-address-of-packed-member
-Wno-multichar -Wno-unused -fno-strict-aliasing -fno-optimize-sibling-calls
-mno-sse -fno-omit-frame-pointer -g -finline-limit=6000 -mcmodel=large
-ffreestanding -mno-red-zone -O2 test.c
3. with objdump you can see that the line :
*(p + 0xffffe) = 0xfc;
compile to :
1044: c6 04 25 fe ff 0f 00 movb $0x0,0xffffe
104b: 00
104c: 0f 0b ud2
While if instead p you will use local parameter (define SIMPLE_WRITE and
recompile)
it will keep user code as expected:
1044: c6 04 25 fe ff 0f 00 movb $0xfc,0xffffe
104b: fc
Note that the problam will not occur if -fno-delete-null-pointer-checks will be
added to the compilation parameters.
