wasm2c: use signal handler to detect stack exhaustion #1875
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(Linux distinguishes these as SEGV_ACCERR vs. SEGV_MAPERR in the si_code, but MacOS seems to deliver a SEGV_ACCERR for both.)
…constant On glibc 2.34+ with the _GNU_SOURCE macro, SIGSTKSZ is no longer a constant (https://sourceware.org/pipermail/libc-alpha/2021-August/129718.html). Convert the "alt stack" to a runtime-allocated array, and add wasm_rt_init() and wasm_rt_free() endpoints to wasm-rt.h that the embedder must call to set up and clean up the runtime state. (If the embedder doesn't call these, OOB and exhaustion will result in an uncaught segfault.)
This was referenced Mar 31, 2022
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Use the signal-handler method to detect and recover from stack exhaustion, in addition to OOB accesses. This eliminates the global
wasm_rt_call_stack_depthand the need to increment/decrement it on function entries and exits. Eliminating this global variable is helpful for module instancing and for running parallel invocations in a thread-safe manner.(The catch is that MacOS doesn't seem to make it easy to distinguish OOB vs. exhaustion, so these trap codes have to be merged on MacOS and perhaps other BSDs. On Linux, it's possible to tell them apart based on the si_code of the SIGSEGV.)