[sqlite] Source Error in EXPLAIN PLAN (for busted compilers)

[Keith Medcalf]

SQLITE_PRIVATE void sqlite3ExplainBegin(Vdbe *pVdbe){
  if( pVdbe ){
    sqlite3BeginBenignMalloc();
    Explain *p = sqlite3_malloc( sizeof(Explain) );
    if( p ){
      memset(p, 0, sizeof(*p));
      p->pVdbe = pVdbe;
      sqlite3_free(pVdbe->pExplain);
      pVdbe->pExplain = p;
      sqlite3StrAccumInit(&p->str, p->zBase, sizeof(p->zBase),
                          SQLITE_MAX_LENGTH);
      p->str.useMalloc = 2;
    }else{
      sqlite3EndBenignMalloc();
    }
  }
}

MSVC compilers do not like constructs which allocate locals on the stack except 
immediately after the initiation of a code block.  Perhaps fixed in later 
versions of the compiler, perhaps not, or perhaps there is a magic incantation 
to make the compiler behave properly.  In any case, the slight modification 
does not affect the semantics of the code.

This can be fixed as follows, so that even primitive compilers will not 
complain:

SQLITE_PRIVATE void sqlite3ExplainBegin(Vdbe *pVdbe){
  if( pVdbe ){
    Explain *p;
    sqlite3BeginBenignMalloc();
    p = sqlite3_malloc( sizeof(Explain) );
    if( p ){
      memset(p, 0, sizeof(*p));
      p->pVdbe = pVdbe;
      sqlite3_free(pVdbe->pExplain);
      pVdbe->pExplain = p;
      sqlite3StrAccumInit(&p->str, p->zBase, sizeof(p->zBase),
                          SQLITE_MAX_LENGTH);
      p->str.useMalloc = 2;
    }else{
      sqlite3EndBenignMalloc();
    }
  }
}

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