Other Parts Discussed in Thread: MSP430FR5994
Tool/software: TI C/C++ Compiler
Was using a MSP430FR5994 to check the limits on the heap size supported by the TI MSP430 compiler, with the project configured to use the 208 Kbyte FRAM2 region for the heap and the data model set to large.
One test involved determining the maximum size allocation malloc() would return when the heap was empty.
With the TI v17.9.0 compiler the maximum size allocation was 32758 bytes which was lower than expected and only part of the heap. Whereas with the TI v18.1.0 compiler the maximum size allocation was 212988 bytes.
On investigation both compiler versions have the same check_alloc_size() call at the start of malloc() in the RTS memory.c source file:
/*****************************************************************************/
/* */
/* CHECK_ALLOC_SIZE - Verify that an allocation of the requested size is */
/* possible without an overflow during the process. */
/* */
/*****************************************************************************/
inline static int check_alloc_size(size_t size)
{
/*-----------------------------------------------------------------------*/
/* Make sure the value of size is small enough that we will not overflow */
/* the memsz_t type in the malloc/realloc calculations. SDSCM00049633. */
/*-----------------------------------------------------------------------*/
if (size > (MEMSZ_MAX - OVERHEAD - MINSIZE - 1))
return 0;
return 1;
}
void *malloc(size_t size)
{
memsz_t allocsize;
PACKET *current, *next, *prev;
if (check_alloc_size(size) == 0) return 0;
allocsize = (memsz_t)size;
The TI v17.9.0 compiler generates the following for check_alloc_size():
malloc(): 004000: 144A PUSHM.A #5,R10 209 if (size > (MEMSZ_MAX - OVERHEAD - MINSIZE - 1)) 004002: 930D TST.W R13 004004: 2029 JNE ($C$L18) 004006: 903C 7FF7 CMP.W #0x7ff7,R12 00400a: 2C26 JHS ($C$L18) 265 allocsize = (memsz_t)size;
Whereas the TI v18.1..0 compiler generates the following for check_alloc_size():
malloc():
004000: 144A PUSHM.A #5,R10
209 if (size > (MEMSZ_MAX - OVERHEAD - MINSIZE - 1))
004002: 903D 7FFF CMP.W #0x7fff,R13
004006: 2804 JLO ($C$L11)
004008: 2029 JNE ($C$L19)
00400a: 903C FFF7 CMP.W #0xfff7,R12
00400e: 2C26 JHS ($C$L19)
265 allocsize = (memsz_t)size;
$C$L11:
The TI v17.9.0 compiler appears to have generated incorrect code for check_alloc_size(), in that it is checking for a maximum size of 0x7FF6 rather than 0x7FFFFFF6. Is this a problem with how the TI v17.9.0 compiler handles comparisons against constants in the large data model?
While the problem was found in the malloc() implementation in the RTS not sure under which other conditions incorrect comparisons could occur.
The example project is attached MSP430FR5994_max_heap_size.zip
