
  success (either via a returned integer value or in the global
  variable <TT
CLASS="VARNAME"
>SPI_result</TT
>, as described below).  On
  error, a negative result or <TT
CLASS="SYMBOL"
>NULL</TT
> will be returned.
 </P
><P
>  Source code files that use SPI must include the header file
  <TT
CLASS="FILENAME"
>executor/spi.h</TT
>.
 </P
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