#3631 misaligned access in codegen for mos6502 port

[Philipp Klaus Krause]

Using sanitizers, I found a misaligned access in code generation of the mos6502 port:

gen.c:578:19: runtime error: member access within misaligned address 0x5651ea9baf51 for type 'struct reg_info', which requires 8 byte alignment

[Gabriele Gorla]

I just did a clean build using GCC 12 from debian using the sanitizer flags and run the regression but I cannot reproduce the issue.
Are there any specific steps to reproduce the issue?

[Philipp Klaus Krause]

I just reproduced the issue on my Debian GNU/Linux testing system on amd64 using GCC 13.2.0.

SDCC was configured via:

./configure CC="gcc -fsanitize=undefined" CXX="g++ -fsanitize=undefined" LDFLAGS="-fsanitize=undefined"

And I see the error message when compiling the library:

/home/philipp/sdcc-trunk/sdcc/bin/sdcc -I./../../include -I. --std-c23  -mmos6502 --max-allocs-per-node 25000 --opt-code-speed -c atomic_flag_test_and_set.c -o atomic_flag_test_and_set.rel
test . = . || cp __sdcc_indirect_jsr.s .
../../../bin/sdas6500 -plosgff __sdcc_indirect_jsr.s
test . = . || rm __sdcc_indirect_jsr.s
/home/philipp/sdcc-trunk/sdcc/bin/sdcc -I./../../include -I. --std-c23  -mmos6502 --max-allocs-per-node 25000 --opt-code-speed -c ../_atof.c -o _atof.rel
gen.c:582:19: runtime error: member access within misaligned address 0x5627133b7181 for type 'struct reg_info', which requires 8 byte alignment
0x5627133b7181: note: pointer points here
 00 00 00  00 5f 61 74 6f 66 5f 69  65 78 70 5f 31 30 30 30  30 5f 35 37 00 00 00 00  00 00 00 00 00
              ^

[Gabriele Gorla]

yep, it was a bad pointer.
Code was dereferencing an AOP register before checking if it was actually a register.
should be fixed with [r14497]