py: Allow lexer to raise exceptions during construction.

This patch refactors the error handling in the lexer, to simplify it (ie
reduce code size).

A long time ago, when the lexer/parser/compiler were first written, the
lexer and parser were designed so they didn't use exceptions (ie nlr) to
report errors but rather returned an error code.  Over time that has
gradually changed, the parser in particular has more and more ways of
raising exceptions.  Also, the lexer never really handled all errors without
raising, eg there were some memory errors which could raise an exception
(and in these rare cases one would get a fatal nlr-not-handled fault).

This patch accepts the fact that the lexer can raise exceptions in some
cases and allows it to raise exceptions to handle all its errors, which are
for the most part just out-of-memory errors during construction of the
lexer.  This makes the lexer a bit simpler, and also the persistent code
stuff is simplified.

What this means for users of the lexer is that calls to it must be wrapped
in a nlr handler.  But all uses of the lexer already have such an nlr
handler for the parser (and compiler) so that doesn't put any extra burden
on the callers.

1 files changed, 5 insertions, 26 deletions

diff --git a/py/lexer.c b/py/lexer.c
index 9dcdd19eb..fadaee6f3 100644
--- a/py/lexer.c
+++ b/py/lexer.c
@@ -699,13 +699,7 @@ void mp_lexer_to_next(mp_lexer_t *lex) {
 }
 
 mp_lexer_t *mp_lexer_new(qstr src_name, mp_reader_t reader) {
-    mp_lexer_t *lex = m_new_obj_maybe(mp_lexer_t);
-
-    // check for memory allocation error
-    if (lex == NULL) {
-        reader.close(reader.data);
-        return NULL;
-    }
+    mp_lexer_t *lex = m_new_obj(mp_lexer_t);
 
     lex->source_name = src_name;
     lex->reader = reader;
@@ -715,16 +709,9 @@ mp_lexer_t *mp_lexer_new(qstr src_name, mp_reader_t reader) {
     lex->nested_bracket_level = 0;
     lex->alloc_indent_level = MICROPY_ALLOC_LEXER_INDENT_INIT;
     lex->num_indent_level = 1;
-    lex->indent_level = m_new_maybe(uint16_t, lex->alloc_indent_level);
+    lex->indent_level = m_new(uint16_t, lex->alloc_indent_level);
     vstr_init(&lex->vstr, 32);
 
-    // check for memory allocation error
-    // note: vstr_init above may fail on malloc, but so may mp_lexer_to_next below
-    if (lex->indent_level == NULL) {
-        mp_lexer_free(lex);
-        return NULL;
-    }
-
     // store sentinel for first indentation level
     lex->indent_level[0] = 0;
 
@@ -764,9 +751,7 @@ mp_lexer_t *mp_lexer_new(qstr src_name, mp_reader_t reader) {
 
 mp_lexer_t *mp_lexer_new_from_str_len(qstr src_name, const char *str, size_t len, size_t free_len) {
     mp_reader_t reader;
-    if (!mp_reader_new_mem(&reader, (const byte*)str, len, free_len)) {
-        return NULL;
-    }
+    mp_reader_new_mem(&reader, (const byte*)str, len, free_len);
     return mp_lexer_new(src_name, reader);
 }
 
@@ -774,10 +759,7 @@ mp_lexer_t *mp_lexer_new_from_str_len(qstr src_name, const char *str, size_t len
 
 mp_lexer_t *mp_lexer_new_from_file(const char *filename) {
     mp_reader_t reader;
-    int ret = mp_reader_new_file(&reader, filename);
-    if (ret != 0) {
-        return NULL;
-    }
+    mp_reader_new_file(&reader, filename);
     return mp_lexer_new(qstr_from_str(filename), reader);
 }
 
@@ -785,10 +767,7 @@ mp_lexer_t *mp_lexer_new_from_file(const char *filename) {
 
 mp_lexer_t *mp_lexer_new_from_fd(qstr filename, int fd, bool close_fd) {
     mp_reader_t reader;
-    int ret = mp_reader_new_file_from_fd(&reader, fd, close_fd);
-    if (ret != 0) {
-        return NULL;
-    }
+    mp_reader_new_file_from_fd(&reader, fd, close_fd);
     return mp_lexer_new(filename, reader);
 }