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wasi-libc: use __heap_end if available (#14273)

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The symbol was introduced in LLD 15.0.7, as a way to know how
much memory can be allocated:

1095870e8c
https://github.com/WebAssembly/wasi-libc/pull/377
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Frank Denis 2023-01-12 14:48:14 +01:00 committed by GitHub
parent 4b32917646
commit cbbf8c8a2d
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1 changed files with 5 additions and 1 deletions
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6
lib/libc/wasi/emmalloc/emmalloc.c vendored
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@ -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__));
// 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!");
@ -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 = sbrk(0);
if (numBytes <= (size_t)(heap_end - &__heap_base)) {
startPtr = &__heap_base;
endPtr = heap_end;