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[3.13] gh-126554: ctypes: Correctly handle NULL dlsym values (GH-126555) #126861

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@miss-islington miss-islington commented Nov 15, 2024

For dlsym(), a return value of NULL does not necessarily indicate
an error 1.

Therefore, to avoid using stale (or NULL) dlerror() values, we must:

  1. clear the previous error state by calling dlerror()
  2. call dlsym()
  3. call dlerror()

If the return value of dlerror() is not NULL, an error occured.

In ctypes we choose to treat a NULL return value from dlsym()
as a "not found" error. This is the same as the fallback
message we use on Windows, Cygwin or when getting/formatting
the error reason fails.

(cherry picked from commit 8717f79)

Co-authored-by: George Alexopoulos [email protected]
Signed-off-by: Georgios Alexopoulos [email protected]
Signed-off-by: Georgios Alexopoulos [email protected]
Co-authored-by: Peter Bierma [email protected]
Co-authored-by: Bénédikt Tran [email protected]
Co-authored-by: Petr Viktorin [email protected]

…-126555)

For dlsym(), a return value of NULL does not necessarily indicate
an error [1].

Therefore, to avoid using stale (or NULL) dlerror() values, we must:

 1. clear the previous error state by calling dlerror()
 2. call dlsym()
 3. call dlerror()

If the return value of dlerror() is not NULL, an error occured.

In ctypes we choose to treat a NULL return value from dlsym()
as a "not found" error. This is the same as the fallback
message we use on Windows, Cygwin or when getting/formatting
the error reason fails.

[1]: https://man7.org/linux/man-pages/man3/dlsym.3.html

(cherry picked from commit 8717f792f7cc343599dc60daf80630cceb66145b)

Co-authored-by: George Alexopoulos <[email protected]>
Signed-off-by: Georgios Alexopoulos <[email protected]>
Signed-off-by: Georgios Alexopoulos <[email protected]>
Co-authored-by: Peter Bierma <[email protected]>
Co-authored-by: Bénédikt Tran <[email protected]>
Co-authored-by: Petr Viktorin <[email protected]>
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🤖 New build scheduled with the buildbot fleet by @encukou for commit 5b4116e 🤖

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@bedevere-bot bedevere-bot removed the 🔨 test-with-buildbots Test PR w/ buildbots; report in status section label Nov 15, 2024
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4 participants