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Port the fix from #377 to emmmalloc. #378

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Port the fix from #377 to emmmalloc. #378

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6 changes: 5 additions & 1 deletion emmalloc/emmalloc.c
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Original file line number Diff line number Diff line change
Expand Up @@ -56,6 +56,7 @@

// Defind by the linker to have the address of the start of the heap.
extern unsigned char __heap_base;
extern unsigned char __heap_end __attribute__((__weak__));
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Since #394, this should no longer be weak.

In fact, building with MALLOC_IMPL=emmalloc is currently broken due to missing this symbol.


// Behavior of right shifting a signed integer is compiler implementation defined.
static_assert((((int32_t)0x80000000U) >> 31) == -1, "This malloc implementation requires that right-shifting a signed integer produces a sign-extending (arithmetic) shift!");
Expand Down Expand Up @@ -545,7 +546,10 @@ static bool claim_more_memory(size_t numBytes)
// If this is the first time we're called, see if we can use
// the initial heap memory set up by wasm-ld.
if (!listOfAllRegions) {
unsigned char *heap_end = sbrk(0);
unsigned char *heap_end = &__heap_end;
if (heap_end == NULL)
heap_end = (unsigned char*) ((size_t) &__heap_base + (PAGE_SIZE-1) & -PAGE_SIZE);
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Once non-weak, the NULL fallback is not needed, but the dlmalloc code is trapping on end < base.


if (numBytes <= (size_t)(heap_end - &__heap_base)) {
startPtr = &__heap_base;
endPtr = heap_end;
Expand Down