Re: [Tarantool-patches] [PATCH v5 38/52] sql: move MEM flags to mem.c

[Mergen Imeev via Tarantool-patches <tarantool-patches@dev.tarantool.org>]

On new branch I dropped this commit. Please see my answer to
"sql: introduce mem_is_*() functions()".

On Fri, Apr 09, 2021 at 11:25:55PM +0300, Mergen Imeev via Tarantool-patches wrote:
> Thank you for the review! My answers and new patch below.
> 
> 
> On 30.03.2021 02:07, Vladislav Shpilevoy wrote:
> > Thanks for the patch!
> >
> >> diff --git a/src/box/sql/mem.h b/src/box/sql/mem.h
> >> index 70224b55a..8b6f6749d 100644
> >> --- a/src/box/sql/mem.h
> >> +++ b/src/box/sql/mem.h
> >> @@ -563,13 +511,6 @@ columnNullValue(void);
> >>  
> >>  int sqlVdbeMemTooBig(Mem *);
> >>  
> >> -/* Return TRUE if Mem X contains dynamically allocated content - anything
> >> - * that needs to be deallocated to avoid a leak.
> >> - */
> >> -#define VdbeMemDynamic(X)  \
> >> -  (((X)->flags&(MEM_Agg|MEM_Dyn|MEM_Frame))!=0)
> >
> > Why did you remove that? And why don't you have MEM_Agg|MEM_Frame in
> > mem_is_dynamic()?
> Function mem_is_dynamic() shows allocation type of MEM contains STRING or
> VARBINARY. Macro VdbeMemDynamic() shows that MEM should be cleared before
> changing. This macro is not needed now outside of mem.c since all settings there
> should be done using mem_set_*() functions, which clear MEM before changing.
> In mem.c this macro may be added in case we set MEM directly, however we inline
> mem_set_*() only in cases when we know that there is no clearing needed. Not
> sure that this macro is needed after all.
> 
> There is one place where MEM is set without mem_set_*() outside of mem.c - in
> function allocateCursor(). However, the way MEM is used here is so different
> from normal way of using MEM, that I am not sure that VdbeMemDynamic() is
> actually proper there.
> 
> 
> New patch:
> 
> commit 670c9835e020f49a67ee8ade81fbf59dd0062beb
> Author: Mergen Imeev <imeevma@gmail.com>
> Date:   Wed Mar 17 10:19:57 2021 +0300
> 
>     sql: move MEM flags to mem.c
>     
>     This patch moves MEM flags to mem.c. This allow us to have more control
>     over MEM state.
>     
>     Part of #5818
> 
> diff --git a/src/box/sql/mem.c b/src/box/sql/mem.c
> index 2e147291f..52b1891aa 100644
> --- a/src/box/sql/mem.c
> +++ b/src/box/sql/mem.c
> @@ -52,6 +52,57 @@
>  static int
>  sqlVdbeMemGrow(struct Mem *pMem, int n, int preserve);
>  
> +/* One or more of the following flags are set to indicate the validOK
> + * representations of the value stored in the Mem struct.
> + *
> + * If the MEM_Null flag is set, then the value is an SQL NULL value.
> + * No other flags may be set in this case.
> + *
> + * If the MEM_Str flag is set then Mem.z points at a string representation.
> + * Usually this is encoded in the same unicode encoding as the main
> + * database (see below for exceptions). If the MEM_Term flag is also
> + * set, then the string is nul terminated. The MEM_Int and MEM_Real
> + * flags may coexist with the MEM_Str flag.
> + */
> +#define MEM_Null      0x0001	/* Value is NULL */
> +#define MEM_Str       0x0002	/* Value is a string */
> +#define MEM_Int       0x0004	/* Value is an integer */
> +#define MEM_Real      0x0008	/* Value is a real number */
> +#define MEM_Blob      0x0010	/* Value is a BLOB */
> +#define MEM_Bool      0x0020    /* Value is a bool */
> +#define MEM_UInt      0x0040	/* Value is an unsigned integer */
> +#define MEM_Frame     0x0080	/* Value is a VdbeFrame object */
> +#define MEM_Undefined 0x0100	/* Value is undefined */
> +#define MEM_Cleared   0x0200	/* NULL set by OP_Null, not from data */
> +#define MEM_TypeMask  0x83ff	/* Mask of type bits */
> +
> +/* Whenever Mem contains a valid string or blob representation, one of
> + * the following flags must be set to determine the memory management
> + * policy for Mem.z.  The MEM_Term flag tells us whether or not the
> + * string is \000 or \u0000 terminated
> + */
> +#define MEM_Term      0x0400	/* String rep is nul terminated */
> +#define MEM_Dyn       0x0800	/* Need to call Mem.xDel() on Mem.z */
> +#define MEM_Static    0x1000	/* Mem.z points to a static string */
> +#define MEM_Ephem     0x2000	/* Mem.z points to an ephemeral string */
> +#define MEM_Agg       0x4000	/* Mem.z points to an agg function context */
> +#define MEM_Zero      0x8000	/* Mem.i contains count of 0s appended to blob */
> +#define MEM_Subtype   0x10000	/* Mem.eSubtype is valid */
> +#define MEM_Ptr       0x20000	/* Value is a generic pointer */
> +
> +/**
> + * In contrast to Mem_TypeMask, this one allows to get
> + * pure type of memory cell, i.e. without _Dyn/_Zero and other
> + * auxiliary flags.
> + */
> +enum {
> +	MEM_PURE_TYPE_MASK = 0x7f
> +};
> +
> +static_assert(MEM_PURE_TYPE_MASK == (MEM_Null | MEM_Str | MEM_Int | MEM_Real |
> +				     MEM_Blob | MEM_Bool | MEM_UInt),
> +	      "value of type mask must consist of corresponding to memory "\
> +	      "type bits");
>  
>  bool
>  mem_is_null(const struct Mem *mem)
> diff --git a/src/box/sql/mem.h b/src/box/sql/mem.h
> index f17c4bb78..ce5076361 100644
> --- a/src/box/sql/mem.h
> +++ b/src/box/sql/mem.h
> @@ -473,58 +473,6 @@ int
>  mem_compare(const struct Mem *left, const struct Mem *right, int *result,
>  	    enum field_type type, struct coll *coll);
>  
> -/* One or more of the following flags are set to indicate the validOK
> - * representations of the value stored in the Mem struct.
> - *
> - * If the MEM_Null flag is set, then the value is an SQL NULL value.
> - * No other flags may be set in this case.
> - *
> - * If the MEM_Str flag is set then Mem.z points at a string representation.
> - * Usually this is encoded in the same unicode encoding as the main
> - * database (see below for exceptions). If the MEM_Term flag is also
> - * set, then the string is nul terminated. The MEM_Int and MEM_Real
> - * flags may coexist with the MEM_Str flag.
> - */
> -#define MEM_Null      0x0001	/* Value is NULL */
> -#define MEM_Str       0x0002	/* Value is a string */
> -#define MEM_Int       0x0004	/* Value is an integer */
> -#define MEM_Real      0x0008	/* Value is a real number */
> -#define MEM_Blob      0x0010	/* Value is a BLOB */
> -#define MEM_Bool      0x0020    /* Value is a bool */
> -#define MEM_UInt      0x0040	/* Value is an unsigned integer */
> -#define MEM_Frame     0x0080	/* Value is a VdbeFrame object */
> -#define MEM_Undefined 0x0100	/* Value is undefined */
> -#define MEM_Cleared   0x0200	/* NULL set by OP_Null, not from data */
> -#define MEM_TypeMask  0x83ff	/* Mask of type bits */
> -
> -/* Whenever Mem contains a valid string or blob representation, one of
> - * the following flags must be set to determine the memory management
> - * policy for Mem.z.  The MEM_Term flag tells us whether or not the
> - * string is \000 or \u0000 terminated
> - */
> -#define MEM_Term      0x0400	/* String rep is nul terminated */
> -#define MEM_Dyn       0x0800	/* Need to call Mem.xDel() on Mem.z */
> -#define MEM_Static    0x1000	/* Mem.z points to a static string */
> -#define MEM_Ephem     0x2000	/* Mem.z points to an ephemeral string */
> -#define MEM_Agg       0x4000	/* Mem.z points to an agg function context */
> -#define MEM_Zero      0x8000	/* Mem.i contains count of 0s appended to blob */
> -#define MEM_Subtype   0x10000	/* Mem.eSubtype is valid */
> -#define MEM_Ptr       0x20000	/* Value is a generic pointer */
> -
> -/**
> - * In contrast to Mem_TypeMask, this one allows to get
> - * pure type of memory cell, i.e. without _Dyn/_Zero and other
> - * auxiliary flags.
> - */
> -enum {
> -	MEM_PURE_TYPE_MASK = 0x7f
> -};
> -
> -static_assert(MEM_PURE_TYPE_MASK == (MEM_Null | MEM_Str | MEM_Int | MEM_Real |
> -				     MEM_Blob | MEM_Bool | MEM_UInt),
> -	      "value of type mask must consist of corresponding to memory "\
> -	      "type bits");
> -
>  /**
>   * Simple type to str convertor. It is used to simplify
>   * error reporting.
> @@ -555,7 +503,7 @@ registerTrace(int iReg, Mem *p);
>   * Return true if a memory cell is not marked as invalid.  This macro
>   * is for use inside assert() statements only.
>   */
> -#define memIsValid(M)  ((M)->flags & MEM_Undefined)==0
> +#define memIsValid(M) !mem_is_invalid(M)
>  #endif
>  
>  /**
> @@ -589,7 +537,7 @@ int mem_apply_integer_type(struct Mem *);
>  int sqlVdbeMemStringify(struct Mem *);
>  int sqlVdbeMemNulTerminate(struct Mem *);
>  int sqlVdbeMemExpandBlob(struct Mem *);
> -#define ExpandBlob(P) (((P)->flags&MEM_Zero)?sqlVdbeMemExpandBlob(P):0)
> +#define ExpandBlob(P) (mem_is_zerobin(P)? sqlVdbeMemExpandBlob(P) : 0)
>  void sql_value_apply_type(struct Mem *val, enum field_type type);
>  
>  
> @@ -700,13 +648,6 @@ columnNullValue(void);
>  
>  int sqlVdbeMemTooBig(Mem *);
>  
> -/* Return TRUE if Mem X contains dynamically allocated content - anything
> - * that needs to be deallocated to avoid a leak.
> - */
> -#define VdbeMemDynamic(X)  \
> -  (((X)->flags&(MEM_Agg|MEM_Dyn|MEM_Frame))!=0)
> -
> -
>  int sqlMemCompare(const Mem *, const Mem *, const struct coll *);
>  
>  /**
> diff --git a/src/box/sql/vdbe.c b/src/box/sql/vdbe.c
> index 4566606d7..71a827034 100644
> --- a/src/box/sql/vdbe.c
> +++ b/src/box/sql/vdbe.c
> @@ -607,7 +607,6 @@ case OP_SetDiag: {             /* jump */
>  case OP_Gosub: {            /* jump */
>  	assert(pOp->p1>0 && pOp->p1<=(p->nMem+1 - p->nCursor));
>  	pIn1 = &aMem[pOp->p1];
> -	assert(VdbeMemDynamic(pIn1)==0);
>  	memAboutToChange(p, pIn1);
>  	mem_set_uint(pIn1, pOp - aOp);
>  	REGISTER_TRACE(p, pOp->p1, pIn1);
> @@ -649,7 +648,6 @@ case OP_InitCoroutine: {     /* jump */
>  	assert(pOp->p2>=0 && pOp->p2<p->nOp);
>  	assert(pOp->p3>0 && pOp->p3<p->nOp);
>  	pOut = &aMem[pOp->p1];
> -	assert(!VdbeMemDynamic(pOut));
>  	mem_set_uint(pOut, pOp->p3 - 1);
>  	if (pOp->p2) goto jump_to_p2;
>  	break;
> @@ -691,7 +689,6 @@ case OP_EndCoroutine: {           /* in1 */
>   */
>  case OP_Yield: {            /* in1, jump */
>  	pIn1 = &aMem[pOp->p1];
> -	assert(VdbeMemDynamic(pIn1)==0);
>  	int pcDest = (int)pIn1->u.u;
>  	mem_set_uint(pIn1, pOp - aOp);
>  	REGISTER_TRACE(p, pOp->p1, pIn1);