[Bug c/107973] New: wrong warning with -Werror -fsanitize=address

[Bug c/107973] New: wrong warning with -Werror -fsanitize=address

[bernd.edlinger at hotmail dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107973

            Bug ID: 107973
           Summary: wrong warning with -Werror -fsanitize=address
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: bernd.edlinger at hotmail dot de
  Target Milestone: ---

when compiling openssl-1.1.1s with the following workflow:

$ wget https://www.openssl.org/source/openssl-1.1.1s.tar.gz
$ tar xf openssl-1.1.1s.tar.gz
$ cd openssl-1.1.1s
$ ./config  --strict-warnings enable-asan
$ make

I get this unexpected warning (error)

gcc  -I. -Iinclude -fPIC -pthread -m64 -fsanitize=address
-fno-omit-frame-pointer -g -Wa,--noexecstack -Wall -O3 -DDEBUG_UNUSED
-DPEDANTIC -pedantic -Wno-long-long -Wall -Wextra -Wno-unused-parameter
-Wno-missing-field-initializers -Wswitch -Wsign-compare -Wshadow -Wformat
-Wtype-limits -Wundef -Werror -Wmissing-prototypes -Wstrict-prototypes
-DOPENSSL_USE_NODELETE -DL_ENDIAN -DOPENSSL_PIC -DOPENSSL_CPUID_OBJ
-DOPENSSL_IA32_SSE2 -DOPENSSL_BN_ASM_MONT -DOPENSSL_BN_ASM_MONT5
-DOPENSSL_BN_ASM_GF2m -DSHA1_ASM -DSHA256_ASM -DSHA512_ASM -DKECCAK1600_ASM
-DRC4_ASM -DMD5_ASM -DAESNI_ASM -DVPAES_ASM -DGHASH_ASM -DECP_NISTZ256_ASM
-DX25519_ASM -DPOLY1305_ASM -DOPENSSLDIR="\"/usr/local/ssl\""
-DENGINESDIR="\"/usr/local/lib/engines-1.1\"" -DNDEBUG  -MMD -MF
ssl/s3_enc.d.tmp -MT ssl/s3_enc.o -c -o ssl/s3_enc.o ssl/s3_enc.c
In function 'ssl3_generate_key_block',
    inlined from 'ssl3_setup_key_block' at ssl/s3_enc.c:290:11:
ssl/s3_enc.c:48:20: error: writing 1 byte into a region of size 0
[-Werror=stringop-overflow=]
   48 |             buf[j] = c;
      |             ~~~~~~~^~~
ssl/s3_enc.c: In function 'ssl3_setup_key_block':
ssl/s3_enc.c:21:19: note: at offset 16 into destination object 'buf' of size 16
   21 |     unsigned char buf[16], smd[SHA_DIGEST_LENGTH];
      |                   ^~~
cc1: all warnings being treated as errors


this happens with:
gcc version 12.2.1 20221130 (GCC)
gcc version 11.3.1 20221205 (GCC) 
gcc version 10.4.1 20221205 (GCC)

but did not happen with:
gcc version 9.5.0 (GCC)

nor does it happen with:
gcc version 13.0.0 20221130 (experimental) (GCC)

It is pretty annoying because this happens in CI builds
once we change from ubuntu-20.04 (gcc9) to ubuntu-22.04 (gcc11)

[Bug c/107973] wrong warning with -Werror -fsanitize=address

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107973

Martin Liška <marxin at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |aldyh at gcc dot gnu.org,
                   |                            |marxin at gcc dot gnu.org

--- Comment #1 from Martin Liška <marxin at gcc dot gnu.org> ---
Fixed on master since r13-1268-g8c99e307b20c502e, note that sanitizers tens to
increase false-positives of warnings:

https://gcc.gnu.org/onlinedocs/gcc/Instrumentation-Options.html
```
Note that sanitizers tend to increase the rate of false positive warnings, most
notably those around -Wmaybe-uninitialized. We recommend against combining
-Werror and [the use of] sanitizers.

```

[Bug tree-optimization/107973] wrong warning with -Werror -fsanitize=address

[bernd.edlinger at hotmail dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107973

--- Comment #2 from Bernd Edlinger <bernd.edlinger at hotmail dot de> ---
Thanks,

I see a very similar warning with
m68k-linux-gnu-gcc but without sanitizer:

crypto/modes/cfb128.c: In function 'CRYPTO_cfb128_encrypt':
crypto/modes/cfb128.c:117:33: error: writing 1 byte into a region of size 0
[-Werror=stringop-overflow=]
  117 |                         ivec[n] = c;
      |                         ~~~~~~~~^~~
crypto/modes/cfb128.c:27:42: note: at offset 16 into destination object 'ivec'
of size [0, 16]
   27 |                            unsigned char ivec[16], int *num,
      |                            ~~~~~~~~~~~~~~^~~~~~~~
cc1: all warnings being treated as errors