Make getenv thread-safe
#191
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In order to return a non-owning pointer without memory leaks the function needs to use a static variable. When calling it from multiple threads there is a data race during the assignment (and conversion) to this variable. Fix by making it `thread_local`. Fixes #189
Using `bash` puts `/mingw64/bin` first in the path but the compiler from `/c/mingw64/bin` is used. This leads to errors running the tests: "Exit code 0xc0000139" (DLL issue) which are related to the use of `thread_local`. Using the powershell works in all cases.
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There is a bug in GCC for 32bit MinGW until version 11. This causes a use-after free for destruction of `thread_local` variables that crash the application when the destructor accesses any member. In the tests it shows up as exit code/status `-1073741819` i.e. `0xC0000005`. Workaround this by not destructing the `stackstring` instance used to hold the value of the last `getenv` result. In the case where any call to `getenv` of a thread yielded a large value heap memory will be allocated and not freed due to this missing destructor call causing a memory leak, possibly for each thread. However values up to some length are stored on stack memory and hence the missing destructor call does not cause a memory leak as the type is essentially trivial in this state. See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83562 Fixed by https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=7fc0f78c3f43af1967cb7b1ee8f4947f3b890aa2
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Codecov ReportAll modified and coverable lines are covered by tests ✅
Additional details and impacted files@@ Coverage Diff @@
## develop #191 +/- ##
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Coverage 99.47% 99.47%
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Files 34 34
Lines 3460 3460
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Hits 3442 3442
Misses 18 18
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In order to return a non-owning pointer without memory leaks the function needs to use a static variable.
When calling it from multiple threads there is a data race during the assignment (and conversion) to this variable.
Fix by making it
thread_local.Fixes #189