Reset options to 0 so can call main() multiple times in a row

2 files changed, 13 insertions, 0 deletions

diff --git a/README.md b/README.md
index 7871ca84..e21ed9bc 100644
--- a/README.md
+++ b/README.md
@@ -66,6 +66,13 @@ cross-compilation environment.  See also
 ["Cross compilation"](https://github.com/jqlang/jq/wiki/Cross-compilation) on
 the wiki.
 
+To compile jq to WebAssembly, install the [Emscripten SDK](https://emscripten.org/docs/getting_started/downloads.html), then:
+
+    git submodule update --init # if building from git to get oniguruma
+    autoreconf -i               # if building from git
+    emconfigure ./configure --with-oniguruma=builtin --disable-maintainer-mode
+    emmake make EXEEXT=.js CFLAGS="-O2" LDFLAGS="-s EXPORTED_RUNTIME_METHODS=['callMain']"
+
 
 # Community
 
diff --git a/src/main.c b/src/main.c
index 3c5133d7..49cd0ed1 100644
--- a/src/main.c
+++ b/src/main.c
@@ -292,6 +292,12 @@ int main(int argc, char* argv[]) {
   _setmode(fileno(stderr), _O_TEXT | _O_U8TEXT);
 #endif
 
+#ifdef __EMSCRIPTEN__
+  /* When compiling to WebAssembly with Emscripten, reset options to ensure we can
+     call main() multiple times without reinitializing the WebAssembly module. */
+  options = 0;
+#endif
+
   if (argc) progname = argv[0];
 
   jq = jq_init();