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Warnings on the current main branch #108562

Closed as not planned
Closed as not planned
Warnings on the current main branch#108562
Labels
buildThe build process and cross-buildtype-bugAn unexpected behavior, bug, or error

Description

@skirpichev
skirpichev
opened on Aug 28, 2023

Bug report

CPython versions tested on:

CPython main branch

Operating systems tested on:

Linux

Output from running 'python -VV' on the command line:

Python 3.13.0a0 (main, Aug 28 2023, 13:54:29) [GCC 12.2.0]

A clear and concise description of the bug:

With

$ # Mon Aug 28 13:44:26 MSK 2023
$ wget https://github.com/python/cpython/archive/refs/heads/main.zip
$ unzip -x main.zip
$ cd cpython-main/
$ ./configure -q && make -s

Build is successful, but I see a bunch of warnings:

In function ‘_io_FileIO_close_impl’,
    inlined from ‘_io_FileIO_close’ at ./Modules/_io/clinic/fileio.c.h:34:12:
./Modules/_io/fileio.c:170:9: warning: ‘exc’ may be used uninitialized [-Wmaybe-uninitialized]
  170 |         _PyErr_ChainExceptions1(exc);
      |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
./Modules/_io/fileio.c: In function ‘_io_FileIO_close’:
./Modules/_io/fileio.c:155:15: note: ‘exc’ was declared here
  155 |     PyObject *exc;
      |               ^~~
Note: Deepfreeze may have added some global objects,
      so run 'make regen-global-objects' if necessary.
In function ‘word_to_string’,
    inlined from ‘coeff_to_string’ at ./Modules/_decimal/libmpdec/io.c:410:13,
    inlined from ‘_mpd_to_string’ at ./Modules/_decimal/libmpdec/io.c:611:18:
./Modules/_decimal/libmpdec/io.c:348:40: warning: writing 1 byte into a region of size 0 [-Wstringop-overflow=]
  348 |         if (s == dot) *s++ = '.'; *s++ = '0' + (char)(x / d); x %= d
      |                                   ~~~~~^~~~~~~~~~~~~~~~~~~~~
./Modules/_decimal/libmpdec/io.c:359:14: note: in expansion of macro ‘EXTRACT_DIGIT’
  359 |     case 15: EXTRACT_DIGIT(s, x, 100000000000000ULL, dot);
      |              ^~~~~~~~~~~~~
./Modules/_decimal/libmpdec/io.c:348:40: warning: writing 1 byte into a region of size 0 [-Wstringop-overflow=]
  348 |         if (s == dot) *s++ = '.'; *s++ = '0' + (char)(x / d); x %= d
      |                                   ~~~~~^~~~~~~~~~~~~~~~~~~~~
./Modules/_decimal/libmpdec/io.c:360:14: note: in expansion of macro ‘EXTRACT_DIGIT’
  360 |     case 14: EXTRACT_DIGIT(s, x, 10000000000000ULL, dot);
      |              ^~~~~~~~~~~~~
./Modules/_decimal/libmpdec/io.c:348:40: warning: writing 1 byte into a region of size 0 [-Wstringop-overflow=]
  348 |         if (s == dot) *s++ = '.'; *s++ = '0' + (char)(x / d); x %= d
      |                                   ~~~~~^~~~~~~~~~~~~~~~~~~~~
./Modules/_decimal/libmpdec/io.c:361:14: note: in expansion of macro ‘EXTRACT_DIGIT’
  361 |     case 13: EXTRACT_DIGIT(s, x, 1000000000000ULL, dot);
      |              ^~~~~~~~~~~~~
[...]

N.B. second type of warnings (expansions of EXTRACT_DIGIT) seems to be related to the gcc-12. The first I've seen on the Debian Buster (with gcc-10 per default).

Linked PRs

Activity

  1. skirpichev
    added
    type-bugAn unexpected behavior, bug, or error
    on Aug 28, 2023

  2. sobolevn commented on Aug 28, 2023

    @sobolevn
    sobolevn
    on Aug 28, 2023
    Member

    On macos it produces a different result:

    » ./configure -q && make -s
Python/optimizer.c:388:9: warning: variable 'reserved' set but not used [-Wunused-but-set-variable]
    int reserved = 0;
        ^
1 warning generated.
Note: Deepfreeze may have added some global objects,
      so run 'make regen-global-objects' if necessary.
./Modules/readline.c:1257:21: warning: incompatible function pointer types assigning to 'Function *' (aka 'int (*)(const char *, int)') from 'int (void)' [-Wincompatible-function-pointer-types]
    rl_startup_hook = on_startup_hook;
                    ^ ~~~~~~~~~~~~~~~
./Modules/readline.c:1259:23: warning: incompatible function pointer types assigning to 'Function *' (aka 'int (*)(const char *, int)') from 'int (void)' [-Wincompatible-function-pointer-types]
    rl_pre_input_hook = on_pre_input_hook;
                      ^ ~~~~~~~~~~~~~~~~~
2 warnings generated.
Undefined symbols for architecture arm64:
  "__Py_DECREF_DecRefTotal", referenced from:
      _test_open_code_hook in _testembed.o
      _test_unicode_id_init in _testembed.o
      _Py_DECREF in _testembed.o
  "__Py_NegativeRefcount", referenced from:
      _test_open_code_hook in _testembed.o
      _test_unicode_id_init in _testembed.o
      _Py_DECREF in _testembed.o
ld: symbol(s) not found for architecture arm64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make: *** [Programs/_testembed] Error 1

  3. skirpichev commented on Aug 29, 2023

    @skirpichev
    skirpichev
    on Aug 29, 2023
    MemberAuthor

    @sobolevn, in my case the build was successful. I did update of the bugreport in case it wasn't clear.

  4. skrah commented on Jan 29, 2024

    @skrah
    skrah
    on Jan 29, 2024
    Contributor

    The libmpdec warning is a false positive due to -fno-strict-overflow:

    https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113664

    libmpdec very much supports strict overflow, so adding -fstrict=overflow to LIBMPDEC_CFLAGS should fix this.

  5. skirpichev commented on Jan 30, 2024

    @skirpichev
    skirpichev
    on Jan 30, 2024
    MemberAuthor

    @skrah, maybe I miss something, but with --with-strict-overflow I still see warnings:

    $ ./configure -q --with-strict-overflow && make -s
In function ‘word_to_string’,
    inlined from ‘coeff_to_string’ at ./Modules/_decimal/libmpdec/io.c:410:13,
    inlined from ‘_mpd_to_string’ at ./Modules/_decimal/libmpdec/io.c:611:18:
./Modules/_decimal/libmpdec/io.c:348:40: warning: array subscript 0 is outside array bounds of ‘char[0]’ [-Warray-bounds]
  348 |         if (s == dot) *s++ = '.'; *s++ = '0' + (char)(x / d); x %= d
      |                                   ~~~~~^~~~~~~~~~~~~~~~~~~~~
./Modules/_decimal/libmpdec/io.c:355:14: note: in expansion of macro ‘EXTRACT_DIGIT’
  355 |     case 19: EXTRACT_DIGIT(s, x, 1000000000000000000ULL, dot);
      |              ^~~~~~~~~~~~~
In function ‘word_to_string’,
    inlined from ‘coeff_to_string’ at ./Modules/_decimal/libmpdec/io.c:410:13,
    inlined from ‘_mpd_to_string’ at ./Modules/_decimal/libmpdec/io.c:607:18:
./Modules/_decimal/libmpdec/io.c:348:40: warning: array subscript 0 is outside array bounds of ‘char[0]’ [-Warray-bounds]
  348 |         if (s == dot) *s++ = '.'; *s++ = '0' + (char)(x / d); x %= d
      |                                   ~~~~~^~~~~~~~~~~~~~~~~~~~~
./Modules/_decimal/libmpdec/io.c:355:14: note: in expansion of macro ‘EXTRACT_DIGIT’
  355 |     case 19: EXTRACT_DIGIT(s, x, 1000000000000000000ULL, dot);
      |              ^~~~~~~~~~~~~
In function ‘word_to_string’,
    inlined from ‘coeff_to_string’ at ./Modules/_decimal/libmpdec/io.c:410:13,
    inlined from ‘_mpd_to_string’ at ./Modules/_decimal/libmpdec/io.c:501:22:
./Modules/_decimal/libmpdec/io.c:348:40: warning: array subscript 0 is outside array bounds of ‘char[0]’ [-Warray-bounds]
  348 |         if (s == dot) *s++ = '.'; *s++ = '0' + (char)(x / d); x %= d
      |                                   ~~~~~^~~~~~~~~~~~~~~~~~~~~
./Modules/_decimal/libmpdec/io.c:355:14: note: in expansion of macro ‘EXTRACT_DIGIT’
  355 |     case 19: EXTRACT_DIGIT(s, x, 1000000000000000000ULL, dot);
      |              ^~~~~~~~~~~~~
./Modules/_decimal/libmpdec/io.c:348:40: warning: array subscript 0 is outside array bounds of ‘char[0]’ [-Warray-bounds]
  348 |         if (s == dot) *s++ = '.'; *s++ = '0' + (char)(x / d); x %= d
      |                                   ~~~~~^~~~~~~~~~~~~~~~~~~~~
./Modules/_decimal/libmpdec/io.c:356:14: note: in expansion of macro ‘EXTRACT_DIGIT’
  356 |     case 18: EXTRACT_DIGIT(s, x, 100000000000000000ULL, dot);
      |              ^~~~~~~~~~~~~
Checked 110 modules (33 built-in, 76 shared, 1 n/a on linux-x86_64, 0 disabled, 0 missing, 0 failed on import)

    PS: _io_FileIO_close_impl() from the original report is already fixed.
    PPS: gcc version was mentioned above:

    $ gcc --version
gcc (Debian 12.2.0-14) 12.2.0

  6. skrah commented on Jan 30, 2024

    @skrah
    skrah
    on Jan 30, 2024
    Contributor

    Indeed, that is another false positive (-Warray-bounds this time). It is already disabled in mpdecimal-4.0.0.

    As explained in the linked gcc issue, the exact warning emitted depends on what path the optimizer takes.
    The key issue in both cases is that gcc does not like the (correct) if (s == dot) check.

    If you compile --with-strict-overflow and apply this patch, it should work:

    diff --git a/Modules/_decimal/libmpdec/io.c b/Modules/_decimal/libmpdec/io.c
index e7bd6ae..adedde7 100644
--- a/Modules/_decimal/libmpdec/io.c
+++ b/Modules/_decimal/libmpdec/io.c
@@ -46,6 +46,7 @@
 
 
 #if defined(__GNUC__) && !defined(__INTEL_COMPILER) && __GNUC__ >= 7
+  #pragma GCC diagnostic ignored "-Warray-bounds"
   #pragma GCC diagnostic ignored "-Wimplicit-fallthrough"
   #pragma GCC diagnostic ignored "-Wmisleading-indentation"
 #endif
  7. skirpichev
    added 2 commits that reference this issue on Jan 30, 2024

    pythongh-108562: fix compiler warnings for bundled libmpdec in the main

    3303b02

    pythongh-108562: fix compiler warnings for bundled libmpdec in the main

    8e514c5

  8. skirpichev commented on Jan 30, 2024

    @skirpichev
    skirpichev
    on Jan 30, 2024
    MemberAuthor

    Thanks, that part was backported. See full patch: #114751

  9. erlend-aasland
    added a commit that references this issue on Mar 3, 2024

    gh-108562: Fix compiler warnings for libmpdec (#114751)

    002a594
  10. erlend-aasland
    added
    buildThe build process and cross-build
    on Mar 3, 2024
  11. erlend-aasland
    closed this as completedon Mar 3, 2024

  12. encukou commented on Mar 4, 2024

    @encukou
    encukou
    on Mar 4, 2024
    Member

    When this PR was merged, LTO buildbots started failing. See for example: https://buildbot.python.org/all/#/builders/29/builds/5844

  13. encukou
    reopened this on Mar 4, 2024

  14. erlend-aasland commented on Mar 4, 2024

    @erlend-aasland
    erlend-aasland
    on Mar 4, 2024
    Contributor

    Ok, can you revert #114751, @encukou?

  15. 8 remaining items

  16. skirpichev
    added a commit that references this issue on Mar 5, 2024

    pythongh-108562: turn off false-positive -Wstringop-overflow in word_…

    4f4aa01

  17. skirpichev commented on Mar 5, 2024

    @skirpichev
    skirpichev
    on Mar 5, 2024
    MemberAuthor

    Alternative fix: #116346

    #116302 works for deadsnakes?

    I think so: https://github.com/deadsnakes/python3.13-nightly/actions/runs/8153413773

  18. erlend-aasland commented on Mar 5, 2024

    @erlend-aasland
    erlend-aasland
    on Mar 5, 2024
    Contributor

    Thanks for the heads-up, Sergey! Closing as resolved.

  19. erlend-aasland
    closed this as completedon Mar 5, 2024

  20. skirpichev commented on Mar 5, 2024

    @skirpichev
    skirpichev
    on Mar 5, 2024
    MemberAuthor

    @erlend-aasland, warnings in the main are present. I think this issue isn't solved.

  21. erlend-aasland
    reopened this on Mar 5, 2024
  22. adorilson
    added 2 commits that reference this issue on Mar 25, 2024

    pythongh-108562: Fix compiler warnings for libmpdec (python#114751)

    b65bb32

    pythongh-108562: Revert enabling -fstrict-overflow for libmpdec (pyth…

    bb2e411
  23. diegorusso
    added 2 commits that reference this issue on Apr 17, 2024

    pythongh-108562: Fix compiler warnings for libmpdec (python#114751)

    38a87a1

    pythongh-108562: Revert enabling -fstrict-overflow for libmpdec (pyth…

    ae18536

  24. skirpichev commented on Oct 6, 2024

    @skirpichev
    skirpichev
    on Oct 6, 2024
    MemberAuthor

    @erlend-aasland, this should be fixed if we update bundled mpdecimal to v4. Does it make sense for you?

  25. erlend-aasland commented on Oct 6, 2024

    @erlend-aasland
    erlend-aasland
    on Oct 6, 2024
    Contributor

    @erlend-aasland, this should be fixed if we update bundled mpdecimal to v4. Does it make sense for you?

    Aren't we trying to unbundle mpdecimal? :)

  26. skirpichev commented on Oct 6, 2024

    @skirpichev
    skirpichev
    on Oct 6, 2024
    MemberAuthor

    Yes, but Debian people removed mpdecimal.

    UPD: ah, no. v4.0.0 doesn't include #116346

  27. skirpichev
    closed this as not plannedon Oct 7, 2024

  28. vstinner commented on Oct 7, 2024

    @vstinner
    vstinner
    on Oct 7, 2024
    Member

    @erlend-aasland:

    Aren't we trying to unbundle mpdecimal? :)

    Right, What's New in Python 3.13 says:

    Pending Removal in Python 3.15: The bundled copy of libmpdecimal.

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