A crappy demo for building C to WebAssembly on macos or linux

hello.c

#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>

int is_empty(char *s) {
    char c;
    for (c = *s; c; s++) {
        if (!isspace(c)) {
            return 0;
        }
    }
    return 1;
}

int main(int argc, char *argv[]) {
    int retval = 0;
    if (argc > 1) {
        printf("Hello,");
        for (int i=1; i<argc; i++) {
            printf(" %s", argv[i]);
        }
        printf("!\n");
    } else {
        char *name = NULL;
        ssize_t len = 0;
        size_t cap = 0;
        printf("Hi there. What's your name?\n> ");
        fflush(stdout);
        len = getline(&name, &cap, stdin);
        if (len < 0) {
            fprintf(stderr, "Something went wrong! Sorry :(\n");
            return 1;
        }
        if (is_empty(name)) {
            printf("You don't have a name? That's cool, me either.\n");
        } else {
            name[len-1] = '!'; // replace trailing "\n" with a null
            printf("Hello, %s\n", name);
        }
        free(name);
    }
}

Makefile

CC=clang
CFLAGS=-Os

WASI_VERSION=12
WASI_VERSION_FULL=$(WASI_VERSION).0

ifeq ($(OS),Windows_NT)
    HOST_OS=mingw
else
    UNAME_S := $(shell uname -s)
    ifeq ($(UNAME_S),Linux)
        HOST_OS = linux
    endif
    ifeq ($(UNAME_S),Darwin)
        HOST_OS = macos
    endif
endif

WASI_RELEASE_BASEURL=https://github.com/WebAssembly/wasi-sdk/releases/download/wasi-sdk-$(WASI_VERSION)
WASI_SDK_TARBALL=wasi-sdk-$(WASI_VERSION_FULL)-$(HOST_OS).tar.gz
WASI_SDK_DIR=wasi-sdk-$(WASI_VERSION_FULL)
WASI_SYSROOT=$(WASI_SDK_DIR)/share/wasi-sysroot
WASI_CC=$(WASI_SDK_DIR)/bin/clang --sysroot=$(WASI_SYSROOT)

all: hello hello.wasm

hello: hello.c
        $(CC) $(CFLAGS) $< -o $@

hello.wasm: hello.c $(WASI_SDK_DIR)
        $(WASI_CC) --sysroot=$(WASI_SYSROOT) $< -o $@

$(WASI_SDK_DIR):
        curl --proto '=https' --tlsv1.2 -sSLf $(WASI_RELEASE_BASEURL)/$(WASI_SDK_TARBALL) | tar -zxvf -

clean:
        @rm -f hello hello.wasm