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Fix race condition in CUtlSymbolTableMT lookup #1807

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Fix race condition in CUtlSymbolTableMT lookup #1807

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11 changes: 11 additions & 0 deletions src/public/tier1/utlsymbol.h
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Original file line number Diff line number Diff line change
Expand Up @@ -139,6 +139,17 @@ class CUtlSymbolTable
unsigned short m_iOffset; // Index into the string pool.
};

// Helper to store search string on the stack for safe thread access
class CStringPoolIndexSearch : public CStringPoolIndex
{
public:
CStringPoolIndexSearch( const char* pString ) : CStringPoolIndex( 0xFFFF, 0xFFFF )
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@dimhotepus dimhotepus Feb 16, 2026

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Nice trick, thanks!

{
m_pUserSearchString = pString;
}
const char* m_pUserSearchString;
};

class CLess
{
public:
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8 changes: 4 additions & 4 deletions src/tier1/utlsymbol.cpp
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Expand Up @@ -142,9 +142,9 @@ bool CUtlSymbolTable::CLess::operator()( const CStringPoolIndex &i1, const CStri
// right now at least, because m_LessFunc is the first member of CUtlRBTree, and m_Lookup
// is the first member of CUtlSymbolTabke, this == pTable
CUtlSymbolTable *pTable = (CUtlSymbolTable *)( (byte *)this - offsetof(CUtlSymbolTable::CTree, m_LessFunc) ) - offsetof(CUtlSymbolTable, m_Lookup );
const char* str1 = (i1 == INVALID_STRING_INDEX) ? pTable->m_pUserSearchString :
const char* str1 = (i1 == INVALID_STRING_INDEX) ? static_cast< const CUtlSymbolTable::CStringPoolIndexSearch& >( i1 ).m_pUserSearchString :
pTable->StringFromIndex( i1 );
const char* str2 = (i2 == INVALID_STRING_INDEX) ? pTable->m_pUserSearchString :
const char* str2 = (i2 == INVALID_STRING_INDEX) ? static_cast< const CUtlSymbolTable::CStringPoolIndexSearch& >( i2 ).m_pUserSearchString :
pTable->StringFromIndex( i2 );

if ( !str1 && str2 )
Expand Down Expand Up @@ -181,11 +181,11 @@ CUtlSymbol CUtlSymbolTable::Find( const char* pString ) const
return CUtlSymbol();

// Store a special context used to help with insertion
m_pUserSearchString = pString;
CStringPoolIndexSearch search( pString );

// Passing this special invalid symbol makes the comparison function
// use the string passed in the context
UtlSymId_t idx = m_Lookup.Find( INVALID_STRING_INDEX );
UtlSymId_t idx = m_Lookup.Find( search );

#ifdef _DEBUG
m_pUserSearchString = NULL;
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