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Backport !1665 “Fix g_module_symbol() under Windows sometimes not succeeding” to glib-2-64

Philip Withnall requested to merge pwithnall/glib:backport-1665-win32-module-glib-2-64 into glib-2-64

g_module_symbol() internally calls CreateToolhelp32Snapshot() which in some circumstances returns ERROR_BAD_LENGTH and according to the docs should lead to CreateToolhelp32Snapshot() being retried by the caller.

This retry logic was missing and for example led to g_module_symbol() not succeeding if another thread happened to call the wrong function at the wrong time.

This got noticed in the g-i build of gtk4 where g-i would call g_module_symbol() on all gtk4 _get_type symbols and while inspecting the properties gtk4 would spawn a thread calling SHGetSpecialFolderLocation() somewhere down the line. During the call to SHGetSpecialFolderLocation() CreateToolhelp32Snapshot() would return with ERROR_BAD_LENGTH for a short period of time and make g_module_symbol() fail, which lead to "Invalid GType function" errors in g-i.

Fixes gtk#3213 (closed)

Trivial backport of !1665 (merged) to glib-2-64.

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