Internals: Add WASI (wasm32-wasip1) build support (#8216) (#8217)

src/V3Os.cpp

@@ -82,7 +82,9 @@ VL_DEFINE_DEBUG_FUNCTIONS;
 # endif
 #else
 # include <sys/time.h>
-# include <sys/wait.h>  // Needed on FreeBSD for WIFEXITED
+# ifndef __wasi__
+#  include <sys/wait.h>  // Needed on FreeBSD for WIFEXITED
+# endif
 # include <unistd.h>  // usleep
 #endif
 // clang-format on
@@ -445,6 +447,12 @@ string V3Os::trueRandom(size_t size) VL_MT_SAFE {
     if (VL_UNCOVERABLE(!BCRYPT_SUCCESS(hr))) {
         v3fatal("Could not acquire random data. Try specifying a key instead.");  // LCOV_EXCL_LINE
     }
+#elif defined(__wasi__)
+    // WASI has no /dev/urandom. getentropy() rejects sizes over 256 bytes,
+    // which is more than any caller asks for, and errors rather than truncates.
+    if (VL_UNCOVERABLE(getentropy(data, size))) {
+        v3fatal("Could not acquire random data. Try specifying a key instead.");  // LCOV_EXCL_LINE
+    }
 #else
     std::ifstream is{"/dev/urandom", std::ios::in | std::ios::binary};
     // This read uses the size of the buffer.
@@ -492,6 +500,11 @@ void V3Os::u_sleep(int64_t usec) {
 // METHODS (sub command)
 
 int V3Os::system(const string& command) {
+#ifdef __wasi__
+    // WASI has no process spawning
+    v3fatal("Running subcommands is not supported on this platform: " << command);
+    return -1;
+#else
     UINFO(1, "Running system: " << command);
     const int ret = ::system(command.c_str());
     if (VL_UNCOVERABLE(ret == -1)) {
@@ -504,6 +517,7 @@ int V3Os::system(const string& command) {
     UINFO(1, command << " returned exit code of " << exit_code);
     UASSERT(exit_code >= 0, "exit code must not be negative");
     return exit_code;
+#endif
 }
 
 void V3Os::selfTest() {