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access TLS cache variable directly and not via a helper function when using compiler with native TLS support to work around an apparent bug in g++

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git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@55501 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
This commit is contained in:
Vadim Zeitlin
2008-09-06 22:12:04 +00:00
parent 36eca86160
commit e810df36b3
2 changed files with 29 additions and 9 deletions
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30
include/wx/string.h
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@@ -594,11 +594,19 @@ private:
unsigned lastUsed;
};
// notice that we must use an accessor function and not a static variable
// because when the TLS variables support is implemented in the library (and
// not by the compiler), the global s_cache variable could be not yet
// initialized when a ctor of another global object is executed and if that
// ctor uses any wxString methods, bad things happen
#ifndef wxHAS_COMPILER_TLS
// we must use an accessor function and not a static variable when the TLS
// variables support is implemented in the library (and not by the compiler)
// because the global s_cache variable could be not yet initialized when a
// ctor of another global object is executed and if that ctor uses any
// wxString methods, bad things happen
//
// however notice that this approach does not work when compiler TLS is used,
// at least not with g++ 4.1.2 under amd64 as it apparently compiles code
// using this accessor incorrectly when optimizations are enabled (-O2 is
// enough) -- luckily we don't need it then neither as static __thread
// variables are initialized by 0 anyhow then and so we can use the variable
// directly
static Cache& GetCache()
{
static wxTLS_TYPE(Cache) s_cache;
@@ -606,14 +614,18 @@ private:
return wxTLS_VALUE(s_cache);
}
static Cache::Element *GetCacheBegin() { return GetCache().cached; }
static Cache::Element *GetCacheEnd() { return GetCacheBegin() + Cache::SIZE; }
static unsigned& LastUsedCacheElement() { return GetCache().lastUsed; }
// this helper struct is used to ensure that GetCache() is called during
// static initialization time, i.e. before any threads creation, as otherwise
// the static s_cache construction inside GetCache() wouldn't be MT-safe
friend struct wxStrCacheInitializer;
#else // wxHAS_COMPILER_TLS
static wxTLS_TYPE(Cache) ms_cache;
static Cache& GetCache() { return wxTLS_VALUE(ms_cache); }
#endif // !wxHAS_COMPILER_TLS/wxHAS_COMPILER_TLS
static Cache::Element *GetCacheBegin() { return GetCache().cached; }
static Cache::Element *GetCacheEnd() { return GetCacheBegin() + Cache::SIZE; }
static unsigned& LastUsedCacheElement() { return GetCache().lastUsed; }
// this is used in debug builds only to provide a convenient function,
// callable from a debugger, to show the cache contents