gh-123011: Fix warn_explicit() with the globals of the main module by serhiy-storchaka · Pull Request #155318 · python/cpython · GitHub

warnings.warn_explicit(module_globals=globals()) failed in the __main__ module:

executed as a script it emitted a spurious DeprecationWarning: Module globals is missing a __spec__.loader, because __main__ has __spec__ set to None;
executed with -m it raised ImportError: loader for spam cannot handle __main__, because __name__ was used instead of __spec__.name;
executed as a command or in the REPL it raised ImportError: '__main__' is not a built-in module, because the built-in importer has no source.

The source line is now optional: an ImportError from the loader is no longer propagated.

The pure Python implementation, which uses linecache, was not affected.

Issue: warn_explicit() issues a warning or an error when used directly in a script #123011

… module The __main__ module executed as a script or a command has __spec__ set to None, so warn_explicit(module_globals=globals()) emitted a spurious DeprecationWarning. It also raised ImportError when the loader was unable to provide the source of the module: when the module was executed with -m (the loader can only handle its own module name) or as a command (the built-in importer has no source).

Thanks @serhiy-storchaka for the PR 🌮🎉.. I'm working now to backport this PR to: 3.13, 3.14, 3.15.
🐍🍒⛏🤖

GH-155989 is a backport of this pull request to the 3.15 branch.

GH-155990 is a backport of this pull request to the 3.14 branch.

GH-155991 is a backport of this pull request to the 3.13 branch.

…_ module (GH-155318) (GH-155991) The __main__ module executed as a script or a command has __spec__ set to None, so warn_explicit(module_globals=globals()) emitted a spurious DeprecationWarning. It also raised ImportError when the loader was unable to provide the source of the module: when the module was executed with -m (the loader can only handle its own module name) or as a command (the built-in importer has no source). (cherry picked from commit f2eaf17) Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>

…_ module (GH-155318) (GH-155990) The __main__ module executed as a script or a command has __spec__ set to None, so warn_explicit(module_globals=globals()) emitted a spurious DeprecationWarning. It also raised ImportError when the loader was unable to provide the source of the module: when the module was executed with -m (the loader can only handle its own module name) or as a command (the built-in importer has no source). (cherry picked from commit f2eaf17) Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>

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HEAD is now at f2eaf174b2505b gh-123011: Fix warn_explicit() with the globals of the __main__ module (GH-155318)
Switched to and reset branch 'main'

configure: WARNING: s390x-ibm-linux-gnu/clang is not supported
configure: WARNING:

Platform "s390x-ibm-linux-gnu" with compiler "clang" is not supported by the
CPython core team, see https://peps.python.org/pep-0011/ for more information.


Objects/unicodeobject.c:4906:1: warning: unused function 'ctz' [-Wunused-function]
 4906 | ctz(size_t v)
      | ^~~
1 warning generated.
In file included from ./Modules/expat/xmltok.c:312:
./Modules/expat/xmltok_impl.c:285:5: warning: fallthrough annotation in unreachable code [-Wunreachable-code-fallthrough]
  285 |     CHECK_NMSTRT_CASES(enc, ptr, end, nextTokPtr)
      |     ^
./Modules/expat/xmltok_impl.c:118:5: note: expanded from macro 'CHECK_NMSTRT_CASES'
  118 |     EXPAT_FALLTHROUGH;                                                         \
      |     ^
./Modules/expat/fallthrough.h:47:33: note: expanded from macro 'EXPAT_FALLTHROUGH'
   47 | #      define EXPAT_FALLTHROUGH __attribute__((fallthrough))
      |                                 ^
In file included from ./Modules/expat/xmltok.c:312:
./Modules/expat/xmltok_impl.c:292:7: warning: fallthrough annotation in unreachable code [-Wunreachable-code-fallthrough]
  292 |       CHECK_NAME_CASES(enc, ptr, end, nextTokPtr)
      |       ^
./Modules/expat/xmltok_impl.c:89:5: note: expanded from macro 'CHECK_NAME_CASES'
   89 |     EXPAT_FALLTHROUGH;                                                         \
      |     ^
./Modules/expat/fallthrough.h:47:33: note: expanded from macro 'EXPAT_FALLTHROUGH'
   47 | #      define EXPAT_FALLTHROUGH __attribute__((fallthrough))
      |                                 ^
In file included from ./Modules/expat/xmltok.c:312:
./Modules/expat/xmltok_impl.c:438:5: warning: fallthrough annotation in unreachable code [-Wunreachable-code-fallthrough]
  438 |     CHECK_NMSTRT_CASES(enc, ptr, end, nextTokPtr)
      |     ^
./Modules/expat/xmltok_impl.c:118:5: note: expanded from macro 'CHECK_NMSTRT_CASES'
  118 |     EXPAT_FALLTHROUGH;                                                         \
      |     ^
./Modules/expat/fallthrough.h:47:33: note: expanded from macro 'EXPAT_FALLTHROUGH'
   47 | #      define EXPAT_FALLTHROUGH __attribute__((fallthrough))
      |                                 ^
In file included from ./Modules/expat/xmltok.c:312:
./Modules/expat/xmltok_impl.c:445:7: warning: fallthrough annotation in unreachable code [-Wunreachable-code-fallthrough]
  445 |       CHECK_NAME_CASES(enc, ptr, end, nextTokPtr)
      |       ^
./Modules/expat/xmltok_impl.c:89:5: note: expanded from macro 'CHECK_NAME_CASES'
   89 |     EXPAT_FALLTHROUGH;                                                         \
      |     ^
./Modules/expat/fallthrough.h:47:33: note: expanded from macro 'EXPAT_FALLTHROUGH'
   47 | #      define EXPAT_FALLTHROUGH __attribute__((fallthrough))
      |                                 ^
In file included from ./Modules/expat/xmltok.c:312:
./Modules/expat/xmltok_impl.c:551:5: warning: fallthrough annotation in unreachable code [-Wunreachable-code-fallthrough]
  551 |     CHECK_NMSTRT_CASES(enc, ptr, end, nextTokPtr)
      |     ^
./Modules/expat/xmltok_impl.c:118:5: note: expanded from macro 'CHECK_NMSTRT_CASES'
  118 |     EXPAT_FALLTHROUGH;                                                         \
      |     ^
./Modules/expat/fallthrough.h:47:33: note: expanded from macro 'EXPAT_FALLTHROUGH'
   47 | #      define EXPAT_FALLTHROUGH __attribute__((fallthrough))
      |                                 ^
In file included from ./Modules/expat/xmltok.c:312:
./Modules/expat/xmltok_impl.c:560:7: warning: fallthrough annotation in unreachable code [-Wunreachable-code-fallthrough]
  560 |       CHECK_NAME_CASES(enc, ptr, end, nextTokPtr)
      |       ^
./Modules/expat/xmltok_impl.c:89:5: note: expanded from macro 'CHECK_NAME_CASES'
   89 |     EXPAT_FALLTHROUGH;                                                         \
      |     ^
./Modules/expat/fallthrough.h:47:33: note: expanded from macro 'EXPAT_FALLTHROUGH'
   47 | #      define EXPAT_FALLTHROUGH __attribute__((fallthrough))
      |                                 ^
In file included from ./Modules/expat/xmltok.c:312:
./Modules/expat/xmltok_impl.c:582:7: warning: fallthrough annotation in unreachable code [-Wunreachable-code-fallthrough]
  582 |       CHECK_NAME_CASES(enc, ptr, end, nextTokPtr)
      |       ^
./Modules/expat/xmltok_impl.c:89:5: note: expanded from macro 'CHECK_NAME_CASES'
   89 |     EXPAT_FALLTHROUGH;                                                         \
      |     ^
./Modules/expat/fallthrough.h:47:33: note: expanded from macro 'EXPAT_FALLTHROUGH'
   47 | #      define EXPAT_FALLTHROUGH __attribute__((fallthrough))
      |                                 ^
In file included from ./Modules/expat/xmltok.c:312:
./Modules/expat/xmltok_impl.c:593:9: warning: fallthrough annotation in unreachable code [-Wunreachable-code-fallthrough]
  593 |         CHECK_NMSTRT_CASES(enc, ptr, end, nextTokPtr)
      |         ^
./Modules/expat/xmltok_impl.c:118:5: note: expanded from macro 'CHECK_NMSTRT_CASES'
  118 |     EXPAT_FALLTHROUGH;                                                         \
      |     ^
./Modules/expat/fallthrough.h:47:33: note: expanded from macro 'EXPAT_FALLTHROUGH'
   47 | #      define EXPAT_FALLTHROUGH __attribute__((fallthrough))
      |                                 ^
In file included from ./Modules/expat/xmltok.c:312:
./Modules/expat/xmltok_impl.c:690:11: warning: fallthrough annotation in unreachable code [-Wunreachable-code-fallthrough]
  690 |           CHECK_NMSTRT_CASES(enc, ptr, end, nextTokPtr)
      |           ^
./Modules/expat/xmltok_impl.c:118:5: note: expanded from macro 'CHECK_NMSTRT_CASES'
  118 |     EXPAT_FALLTHROUGH;                                                         \
      |     ^
./Modules/expat/fallthrough.h:47:33: note: expanded from macro 'EXPAT_FALLTHROUGH'
   47 | #      define EXPAT_FALLTHROUGH __attribute__((fallthrough))
      |                                 ^
In file included from ./Modules/expat/xmltok.c:312:
./Modules/expat/xmltok_impl.c:735:5: warning: fallthrough annotation in unreachable code [-Wunreachable-code-fallthrough]
  735 |     CHECK_NMSTRT_CASES(enc, ptr, end, nextTokPtr)
      |     ^
./Modules/expat/xmltok_impl.c:118:5: note: expanded from macro 'CHECK_NMSTRT_CASES'
  118 |     EXPAT_FALLTHROUGH;                                                         \
      |     ^
./Modules/expat/fallthrough.h:47:33: note: expanded from macro 'EXPAT_FALLTHROUGH'
   47 | #      define EXPAT_FALLTHROUGH __attribute__((fallthrough))
      |                                 ^
In file included from ./Modules/expat/xmltok.c:312:
./Modules/expat/xmltok_impl.c:761:7: warning: fallthrough annotation in unreachable code [-Wunreachable-code-fallthrough]
  761 |       CHECK_NAME_CASES(enc, ptr, end, nextTokPtr)
      |       ^
./Modules/expat/xmltok_impl.c:89:5: note: expanded from macro 'CHECK_NAME_CASES'
   89 |     EXPAT_FALLTHROUGH;                                                         \
      |     ^
./Modules/expat/fallthrough.h:47:33: note: expanded from macro 'EXPAT_FALLTHROUGH'
   47 | #      define EXPAT_FALLTHROUGH __attribute__((fallthrough))
      |                                 ^
In file included from ./Modules/expat/xmltok.c:312:
./Modules/expat/xmltok_impl.c:772:9: warning: fallthrough annotation in unreachable code [-Wunreachable-code-fallthrough]
  772 |         CHECK_NMSTRT_CASES(enc, ptr, end, nextTokPtr)
      |         ^
./Modules/expat/xmltok_impl.c:118:5: note: expanded from macro 'CHECK_NMSTRT_CASES'
  118 |     EXPAT_FALLTHROUGH;                                                         \
      |     ^
./Modules/expat/fallthrough.h:47:33: note: expanded from macro 'EXPAT_FALLTHROUGH'
   47 | #      define EXPAT_FALLTHROUGH __attribute__((fallthrough))
      |                                 ^
In file included from ./Modules/expat/xmltok.c:312:
./Modules/expat/xmltok_impl.c:785:11: warning: fallthrough annotation in unreachable code [-Wunreachable-code-fallthrough]
  785 |           CHECK_NMSTRT_CASES(enc, ptr, end, nextTokPtr)
      |           ^
./Modules/expat/xmltok_impl.c:118:5: note: expanded from macro 'CHECK_NMSTRT_CASES'
  118 |     EXPAT_FALLTHROUGH;                                                         \
      |     ^
./Modules/expat/fallthrough.h:47:33: note: expanded from macro 'EXPAT_FALLTHROUGH'
   47 | #      define EXPAT_FALLTHROUGH __attribute__((fallthrough))
      |                                 ^
In file included from ./Modules/expat/xmltok.c:312:
./Modules/expat/xmltok_impl.c:930:5: warning: fallthrough annotation in unreachable code [-Wunreachable-code-fallthrough]
  930 |     CHECK_NMSTRT_CASES(enc, ptr, end, nextTokPtr)
      |     ^
./Modules/expat/xmltok_impl.c:118:5: note: expanded from macro 'CHECK_NMSTRT_CASES'
  118 |     EXPAT_FALLTHROUGH;                                                         \
      |     ^
./Modules/expat/fallthrough.h:47:33: note: expanded from macro 'EXPAT_FALLTHROUGH'
   47 | #      define EXPAT_FALLTHROUGH __attribute__((fallthrough))
      |                                 ^
In file included from ./Modules/expat/xmltok.c:312:
./Modules/expat/xmltok_impl.c:943:7: warning: fallthrough annotation in unreachable code [-Wunreachable-code-fallthrough]
  943 |       CHECK_NAME_CASES(enc, ptr, end, nextTokPtr)
      |       ^
./Modules/expat/xmltok_impl.c:89:5: note: expanded from macro 'CHECK_NAME_CASES'
   89 |     EXPAT_FALLTHROUGH;                                                         \
      |     ^
./Modules/expat/fallthrough.h:47:33: note: expanded from macro 'EXPAT_FALLTHROUGH'
   47 | #      define EXPAT_FALLTHROUGH __attribute__((fallthrough))
      |                                 ^
In file included from ./Modules/expat/xmltok.c:312:
./Modules/expat/xmltok_impl.c:960:5: warning: fallthrough annotation in unreachable code [-Wunreachable-code-fallthrough]
  960 |     CHECK_NMSTRT_CASES(enc, ptr, end, nextTokPtr)
      |     ^
./Modules/expat/xmltok_impl.c:118:5: note: expanded from macro 'CHECK_NMSTRT_CASES'
  118 |     EXPAT_FALLTHROUGH;                                                         \
      |     ^
./Modules/expat/fallthrough.h:47:33: note: expanded from macro 'EXPAT_FALLTHROUGH'
   47 | #      define EXPAT_FALLTHROUGH __attribute__((fallthrough))
      |                                 ^
In file included from ./Modules/expat/xmltok.c:312:
./Modules/expat/xmltok_impl.c:967:7: warning: fallthrough annotation in unreachable code [-Wunreachable-code-fallthrough]
  967 |       CHECK_NAME_CASES(enc, ptr, end, nextTokPtr)
      |       ^
./Modules/expat/xmltok_impl.c:89:5: note: expanded from macro 'CHECK_NAME_CASES'
   89 |     EXPAT_FALLTHROUGH;                                                         \
      |     ^
./Modules/expat/fallthrough.h:47:33: note: expanded from macro 'EXPAT_FALLTHROUGH'
   47 | #      define EXPAT_FALLTHROUGH __attribute__((fallthrough))
      |                                 ^
In file included from ./Modules/expat/xmltok.c:312:
./Modules/expat/xmltok_impl.c:1202:7: warning: fallthrough annotation in unreachable code [-Wunreachable-code-fallthrough]
 1202 |       CHECK_NAME_CASES(enc, ptr, end, nextTokPtr)
      |       ^
./Modules/expat/xmltok_impl.c:89:5: note: expanded from macro 'CHECK_NAME_CASES'
   89 |     EXPAT_FALLTHROUGH;                                                         \
      |     ^
./Modules/expat/fallthrough.h:47:33: note: expanded from macro 'EXPAT_FALLTHROUGH'
   47 | #      define EXPAT_FALLTHROUGH __attribute__((fallthrough))
      |                                 ^
In file included from ./Modules/expat/xmltok.c:312:
./Modules/expat/xmltok_impl.c:1222:11: warning: fallthrough annotation in unreachable code [-Wunreachable-code-fallthrough]
 1222 |           CHECK_NAME_CASES(enc, ptr, end, nextTokPtr)
      |           ^
./Modules/expat/xmltok_impl.c:89:5: note: expanded from macro 'CHECK_NAME_CASES'
   89 |     EXPAT_FALLTHROUGH;                                                         \
      |     ^
./Modules/expat/fallthrough.h:47:33: note: expanded from macro 'EXPAT_FALLTHROUGH'
   47 | #      define EXPAT_FALLTHROUGH __attribute__((fallthrough))
      |                                 ^
19 warnings generated.
ar: unable to copy file 'libpython3.16.a'; reason: No space left on device
make: *** [Makefile:1164: libpython3.16.a] Error 1

chmod: cannot access 'target/': No such file or directory

…_ module (GH-155318) (GH-155989) The __main__ module executed as a script or a command has __spec__ set to None, so warn_explicit(module_globals=globals()) emitted a spurious DeprecationWarning. It also raised ImportError when the loader was unable to provide the source of the module: when the module was executed with -m (the loader can only handle its own module name) or as a command (the built-in importer has no source). (cherry picked from commit f2eaf17) Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>

serhiy-storchaka requested review from FFY00, brettcannon, ericsnowcurrently, ncoghlan and warsaw as code owners August 7, 2026 08:55

bedevere-app Bot added the awaiting core review label Aug 7, 2026

bedevere-app Bot mentioned this pull request Aug 7, 2026

warn_explicit() issues a warning or an error when used directly in a script #123011

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Run the new tests for both implementations

5644f84

serhiy-storchaka added needs backport to 3.13 only security fixes needs backport to 3.14 bugs and security fixes needs backport to 3.15 bugs and security fixes labels Aug 18, 2026

serhiy-storchaka merged commit f2eaf17 into python:main Aug 18, 2026
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serhiy-storchaka deleted the gh-123011-warn-explicit-main branch August 18, 2026 07:29

bedevere-app Bot removed the awaiting core review label Aug 18, 2026

bedevere-app Bot removed the needs backport to 3.15 bugs and security fixes label Aug 18, 2026

bedevere-app Bot removed the needs backport to 3.14 bugs and security fixes label Aug 18, 2026

bedevere-app Bot removed the needs backport to 3.13 only security fixes label Aug 18, 2026

gh-123011: Fix warn_explicit() with the globals of the main module by serhiy-storchaka · Pull Request #155318 · python/cpython · GitHub

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gh-123011: Fix warn_explicit() with the globals of the main module - #155318

gh-123011: Fix warn_explicit() with the globals of the main module#155318
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gh-123011: Fix warn_explicit() with the globals of the __main__ module by serhiy-storchaka · Pull Request #155318 · python/cpython · GitHub

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gh-123011: Fix warn_explicit() with the globals of the __main__ module#155318serhiy-storchaka merged 2 commits intopython:mainpython/cpython:mainfrom serhiy-storchaka:gh-123011-warn-explicit-mainserhiy-storchaka/cpython:gh-123011-warn-explicit-mainCopy head branch name to clipboard

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gh-123011: Fix warn_explicit() with the globals of the main module by serhiy-storchaka · Pull Request #155318 · python/cpython · GitHub

gh-123011: Fix warn_explicit() with the globals of the main module - #155318

gh-123011: Fix warn_explicit() with the globals of the main module#155318
serhiy-storchaka merged 2 commits into
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serhiy-storchaka:gh-123011-warn-explicit-main