Eryk Sun <[email protected]> added the comment:
The warning would not apply to Windows. The environment block is part of the
Process Environment Block (PEB) record, which is protected by a
critical-section lock. The runtime library acquires the PEB lock before
accessing mutable PEB values. For example:
Getting an environment variable:
>>> win32api.GetEnvironmentVariable('foo')
Breakpoint 0 hit
ntdll!RtlQueryEnvironmentVariable:
00007ffc`d737a2f0 48895c2408 mov qword ptr [rsp+8],rbx
ss:00000094`ec9ef470=0000000000000000
RtlQueryEnvironmentVariable acquires the PEB lock (i.e. ntdll!FastPebLock)
before getting the value. The lock is passed to RtlEnterCriticalSection in
register rcx:
0:000> be 2; g
Breakpoint 2 hit
ntdll!RtlEnterCriticalSection:
00007ffc`d737b400 4883ec28 sub rsp,28h
0:000> kc 3
Call Site
ntdll!RtlEnterCriticalSection
ntdll!RtlQueryEnvironmentVariable
KERNELBASE!GetEnvironmentVariableW
0:000> ?? @rcx == (_RTL_CRITICAL_SECTION *)@@(ntdll!FastPebLock)
bool true
Setting an environment variable:
>>> win32api.SetEnvironmentVariable('foo', 'eggs')
Breakpoint 1 hit
ntdll!RtlSetEnvironmentVar:
00007ffc`d73bc7d0 4c894c2420 mov qword ptr [rsp+20h],r9
ss:00000094`ec9ef488=0000000000000000
RtlSetEnvironmentVar acquires the PEB lock before setting the environment
variable:
0:000> be 2; g
Breakpoint 2 hit
ntdll!RtlEnterCriticalSection:
00007ffc`d737b400 4883ec28 sub rsp,28h
0:000> kc 3
Call Site
ntdll!RtlEnterCriticalSection
ntdll!RtlSetEnvironmentVar
KERNELBASE!SetEnvironmentVariableW
0:000> ?? @rcx == (_RTL_CRITICAL_SECTION *)@@(ntdll!FastPebLock)
bool true
----------
nosy: +eryksun
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<https://bugs.python.org/issue39375>
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