Use the new LINUX constant in stdlib (#1270)

Author: Akuli

stdlib/errno.jou

@@ -4,10 +4,12 @@ if WINDOWS:
     declare _errno() -> int*
 elif MACOS:
     declare __error() -> int*
+elif LINUX:
+    declare __errno_location() -> int*
 elif NETBSD:
     declare __errno() -> int*
 else:
-    declare __errno_location() -> int*
+    assert False  # unsupported system
 
 
 @public
@@ -16,10 +18,12 @@ def set_errno(value: int) -> None:
         *_errno() = value
     elif MACOS:
         *__error() = value
+    elif LINUX:
+        *__errno_location() = value
     elif NETBSD:
         *__errno() = value
     else:
-        *__errno_location() = value
+        assert False
 
 
 @public
@@ -28,10 +32,12 @@ def get_errno() -> int:
         return *_errno()
     elif MACOS:
         return *__error()
+    elif LINUX:
+        return *__errno_location()
     elif NETBSD:
         return *__errno()
     else:
-        return *__errno_location()
+        assert False
 
 
 # Convert an error code into a string. Do not modify or free() the returned string.

stdlib/io.jou

@@ -70,15 +70,17 @@ elif MACOS:
     declare global __stdinp: FILE*
     declare global __stdoutp: FILE*
     declare global __stderrp: FILE*
+elif LINUX:
+    declare global stdin: FILE*
+    declare global stdout: FILE*
+    declare global stderr: FILE*
 elif NETBSD:
     if IS_32BIT:
         declare global __sF: byte[88][3]  # sizeof(FILE) == 88
     else:
         declare global __sF: byte[152][3]  # sizeof(FILE) == 152
 else:
-    declare global stdin: FILE*
-    declare global stdout: FILE*
-    declare global stderr: FILE*
+    assert False  # unsupported system
 
 # Returns stdin, the special file for reading keyboard input from terminal.
 @public
@@ -87,10 +89,12 @@ def get_stdin() -> FILE*:
         return __acrt_iob_func(0)
     elif MACOS:
         return __stdinp
+    elif LINUX:
+        return stdin
     elif NETBSD:
         return &__sF[0] as FILE*
     else:
-        return stdin
+        assert False
 
 # Returns stdout, the special file for printing to terminal.
 @public
@@ -99,10 +103,12 @@ def get_stdout() -> FILE*:
         return __acrt_iob_func(1)
     elif MACOS:
         return __stdoutp
+    elif LINUX:
+        return stdout
     elif NETBSD:
         return &__sF[1] as FILE*
     else:
-        return stdout
+        assert False
 
 # Returns stderr, the special file for showing error and warning messages.
 #
@@ -117,10 +123,12 @@ def get_stderr() -> FILE*:
         return __acrt_iob_func(2)
     elif MACOS:
         return __stderrp
+    elif LINUX:
+        return stderr
     elif NETBSD:
         return &__sF[2] as FILE*
     else:
-        return stderr
+        assert False
 
 # Open/close a file for reading or writing. Mode can be e.g. "r", "w",
 # "a", "rb", "wb" or "ab". The meanings of these modes are as in many