Dynamically allocates memory, and can associate allocated heap data with a thread and/or the calling program.
Syntax:
call "CBL_ALLOC_MEM" using mem-pointer
by value mem-size
by value flags
returning status-code
Parameters:
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Using call prototype (see
Key)
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Picture
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mem-pointer
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cblt-pointer
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usage pointer. Must be level 01.
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mem-size
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cblt-os-size
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pic x(4) comp-5 or pic x(8) comp-5 (64-bit native only).
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flags
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cblt-os-flags
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pic x(4) comp-5 or pic x(8) comp-5 (64-bit native only).
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status-code
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See
Library Routines - Key
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On Entry:
-
mem-size
- The number of bytes of memory to allocate.
-
flags
- The type of memory required. You can set the following bits:
Bit 0
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Allocate this memory as shared.
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Bit 1
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Reserved. Must be set to zero.
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Bit 2
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Allocate this memory independently from any calling program. If bit 3 is set it will be freed automatically when the calling
thread ends. If bit 3 is unset it will be freed when the run-unit ends.
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Bit 3
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Allocate this memory as thread local. If bit 2 is unset and there is a direct or indirect (in a mixed language environment)
calling COBOL program, it will be freed when the calling program is canceled or the thread ends - whichever comes first.
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Remaining bits
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Reserved. Must be set to 0.
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On Exit:
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mem-pointer
- A pointer to the memory allocated. The allocated memory is not initialized.
Comments:
The memory allocated is not initialized to any value.
Updates to any shared memory allocated to this function are not serialized or protected by the run-time system; you should use semaphores to maintain the integrity of the data.
If the memory has been allocated by a thread, it is freed when the calling thread terminates.
The maximum size of nonshared memory is restricted only by your operating system (unless the -l run-time switch is set).
The maximum size of shared memory is restricted by the operating system and the run-time system. The run-time tunable, shared_memory_segment_size, can be used to set the maximum size. The size for shared memory allocated using this routine is limited to a maximum of around 64000 bytes.
Bit 1 and bit 2 or bit 3 are mutually exclusive. This is checked and error 181 returned otherwise. If there is no calling program (directly or indirectly in a mixed language environment) bit 2 is ignored.
If bit 2 is not set all standard memory allocated by CBL_ALLOC_MEM is freed when the program that allocated it is canceled (logically or physically), if there is a COBOL program that is directly or indirectly the caller.