VERSION NUMBER needs to be picked up in the __dyn_t-structure

To be able to use dynalloc() a variable of type __dyn_t needs to be
intialized with dyninit():
The __dyn_t structure must be initialized using
the dyninit() macro defined in dyninit.h to ensure the proper "hidden"
version indicator is used. Improper initialization of the __dyn_t
structure will result in undefined behavior.
(z/OS V1R13.0 XL C/C++ Run-Time Library Reference)

SYS1.CEE.SCEEH.H(DYNIT) contains MACRO dyninit:

int dyninit (__dyn_t * dyn_parms);
/* dyninit() zeros out the __dyn_t structure and places the version*/
/* number of the structure into the byte right after __sysout. */
#define dyninit(__dynp)
(
memset((char *)__dynp,'Ö0',sizeof(__dyn_t)),
*((char *)__dynp+1+(2*sizeof(void *))) = 0x01, 0
)
.
In my COBOL pgm __dyn_t structure was set to NULL but no version number
was entered. After checking the compiler listing,
.
* dyninit(&ip);
LA r1,ip(,r13,320)
ST r1,#STRTEMP1(,r13,524)
XC ip(160,r1,0),ip(r1,0)
LA r1,ip(,r13,329)
MVI (*)uchar(r1,0),1
.
i realized that at offset 329-320=9 of the __dyn_t-structure,
due to the word boundary unused first byte the version number,
x'01' needs to be given. Obviously the first version x'00' has not
supported the Request Block Extension.