Set __progname global via static initializer (#16064)

Also sets the related globals `__progname_full`,
`program_invocation_short_name`, and `program_invocation_name`.

Author: guijan

src/library.js

@@ -3485,6 +3485,19 @@ LibraryManager.library = {
     err(UTF8ToString(str));
   },
 
+  // Use program_invocation_short_name and program_invocation_name in compiled
+  // programs. This function is for implementing them.
+  _emscripten_get_progname__sig: 'vii',
+  _emscripten_get_progname: function(str, len) {
+  #if !MINIMAL_RUNTIME
+  #if ASSERTIONS
+    assert(typeof str === 'number');
+    assert(typeof len === 'number');
+  #endif
+    stringToUTF8(thisProgram, str, len);
+  #endif
+  },
+
   emscripten_console_log__sig: 'vi',
   emscripten_console_log: function(str) {
 #if ASSERTIONS

system/lib/libc/musl/src/internal/libc.c

@@ -3,7 +3,9 @@
 struct __libc __libc;
 
 size_t __hwcap;
+#ifndef __EMSCRIPTEN__
 char *__progname=0, *__progname_full=0;
 
 weak_alias(__progname, program_invocation_short_name);
 weak_alias(__progname_full, program_invocation_name);
+#endif

system/lib/libc/musl/src/internal/progname.c

@@ -0,0 +1,38 @@
+/*
+ * Copyright 2022 The Emscripten Authors.  All rights reserved.
+ * Emscripten is available under two separate licenses, the MIT license and the
+ * University of Illinois/NCSA Open Source License.  Both these licenses can be
+ * found in the LICENSE file.
+ */
+
+#ifdef __EMSCRIPTEN__
+#include <limits.h>
+#include <string.h>
+
+char *__progname=0, *__progname_full=0;
+
+weak_alias(__progname, program_invocation_short_name);
+weak_alias(__progname_full, program_invocation_name);
+
+/* See src/library.js for the implementation. */
+extern void _emscripten_get_progname(char*, int);
+
+__attribute__((constructor))
+static void __progname_ctor(void)
+{
+	static char full_path[PATH_MAX];
+	char *basename;
+
+	_emscripten_get_progname(full_path, sizeof(full_path));
+
+	basename = strrchr(full_path, '/');
+	if (basename == NULL) {
+		basename = full_path;
+	} else {
+		basename++;
+	}
+
+	__progname_full = full_path;
+	__progname = basename;
+}
+#endif

tests/other/test_err.out

@@ -1 +1 @@
-(null): hello warning 42
+test_err.js: hello warning 42

tests/other/test_libc_progname.c

@@ -0,0 +1,34 @@
+/*
+ * Copyright 2022 The Emscripten Authors.  All rights reserved.
+ * Emscripten is available under two separate licenses, the MIT license and the
+ * University of Illinois/NCSA Open Source License.  Both these licenses can be
+ * found in the LICENSE file.
+ */
+
+#include <assert.h>
+#include <stdio.h>
+#include <string.h>
+
+extern const char *__progname;
+extern const char *__progname_full;
+
+int main(void) {
+  printf("__progname: %s\n", __progname);
+
+  /* Ensure the pointers aren't NULL. */
+  assert(__progname && __progname_full);
+
+  /* Ensure the basename is contained in the full path. */
+  assert(strstr(__progname_full, __progname));
+
+  /* Ensure the basename contains no path separator. */
+  assert(!strchr(__progname, '/'));
+
+  /* Ensure the full path starts with the root directory. */
+  assert(*__progname_full == '/');
+
+  /* Ensure the full path is a file and not a directory. */
+  assert(__progname_full[strlen(__progname_full)-1] != '/');
+
+  return 0;
+}

tests/other/test_libc_progname.out

@@ -0,0 +1 @@
+__progname: test_libc_progname.js

tests/test_other.py

@@ -461,6 +461,9 @@ def test_multiple_sources(self):
   def test_tsearch(self):
     self.do_other_test('test_tsearch.c')
 
+  def test_libc_progname(self):
+    self.do_other_test('test_libc_progname.c')
+
   def test_combining_object_files(self):
     # Compiling two files with -c will generate separate object files
     self.run_process([EMCC, test_file('twopart_main.cpp'), test_file('twopart_side.c'), '-c'])