[minor enhance] Add macros to identify the Emscripten compiler

Author: martinec

src/base/compiler/version.h

@@ -136,9 +136,17 @@
 #  define UNITEX_COMPILER_CLANG   (__clang_major__       * 10000000 \
                                  + __clang_minor__       * 100000   \
                                  + __clang_patchlevel__  * 1)
+// Emscripten uses Clang/LLVM as its underlying codegen compiler
+#if defined(__EMSCRIPTEN__)
+// UNITEX_COMPILER_IS_CLANG_EMSCRIPTEN
+#  define UNITEX_COMPILER_IS_CLANG_EMSCRIPTEN  1
+#  define UNITEX_COMPILER_CLANG_EMSCRIPTEN\
+                      (__EMSCRIPTEN_major__  * 10000000 \
+                     + __EMSCRIPTEN_minor__  * 100000   \
+                     + __EMSCRIPTEN_tiny__   * 1)
 // Take notice that Apple's Clang distribution bundled with XCode may rewrite
 // __clang_major__ and __clang_minor__ open source Clang distribution' values
-#if defined(__apple_build_version__)
+#elif defined(__apple_build_version__)
 // UNITEX_COMPILER_IS_CLANG_APPLE
 #  define UNITEX_COMPILER_IS_CLANG_APPLE  1
 // __APPLE_CC__   // distinguish  compilers based on the same version of GCC
@@ -568,6 +576,10 @@ const struct /* compiler_name_version_table_t */ {
 // MINGW
 # define UNITEX_COMPILER_NAME         "mingw"
 # define UNITEX_COMPILER_VERSION      UNITEX_COMPILER_MINGW
+#elif UNITEX_COMPILER_IS(CLANG_EMSCRIPTEN)
+// CLANG_EMSCRIPTEN
+# define UNITEX_COMPILER_NAME         "clang.emscripten"
+# define UNITEX_COMPILER_VERSION      UNITEX_COMPILER_CLANG_EMSCRIPTEN
 #elif UNITEX_COMPILER_IS(CLANG_APPLE)
 // CLANG_APPLE
 # define UNITEX_COMPILER_NAME         "clang.apple"

src/base/os/version.h

@@ -204,6 +204,15 @@
 #  if    defined(__pnacl__)
 #   define UNITEX_OS_UNIX_NACL_PORTABLE              1
 #  endif  // !defined(__native_client_nonsfi__)
+// Emscripten behaves like a variant of Unix, so the preprocessor defines unix,
+// _unix and __unix__ are always present when compiling code with Emscripten
+// Note that Native Client sandbox technologies were deprecated on Q4 2019 in
+// favor of WebAssembly. WebAssembly (abbreviated Wasm) is a binary instruction
+// format for a stack-based virtual machine
+# elif   defined(__EMSCRIPTEN__)
+# include <emscripten/version.h>    // __EMSCRIPTEN_major__
+// WebAssembly runtime environments (RE)
+#   define UNITEX_OS_UNIX_WEBASSEMBLY_RE             1
 // Android
 // - UNITEX_OS_UNIX_IS(ANDROID)
 # elif   defined(__ANDROID__)
@@ -659,6 +668,8 @@
 #  define UNITEX_OS_NAME  "unix.apple.osx"
 # elif UNITEX_OS_UNIX_IS(DRAGONFLY)
 #  define UNITEX_OS_NAME  "unix.dragonfly"
+# elif UNITEX_OS_UNIX_IS(WEBASSEMBLY_RE)
+#  define UNITEX_OS_NAME  "unix.webassembly_re"
 # elif UNITEX_OS_UNIX_IS(FREEBSD)
 #  define UNITEX_OS_NAME  "unix.freebsd"
 # elif UNITEX_OS_UNIX_IS(GNU_HURD)

src/base/vendor/whereami/whereami.c

@@ -160,7 +160,7 @@ int WAI_PREFIX(getModulePath)(char* out, int capacity, int* dirname_length)
   return length;
 }
 
-#elif defined(__linux__) || defined(__CYGWIN__) || defined(__sun) || defined(WAI_USE_PROC_SELF_EXE)
+#elif defined(__linux__) || defined(__CYGWIN__) || defined(__sun) || defined(WAI_USE_PROC_SELF_EXE) || defined(__unix__)
 
 #include <stdio.h>
 #include <stdlib.h>