Use char_span for return type of location_get_source_line

location_get_source_line returns a const char * that isn't 0-terminated,
writing back a length through an int * param.

This is error-prone, as all call-sites have to take into account the
lack of 0-termination, and respect the length of the buffer.

It's cleaner to bundle together this pointer+length state into a class,
so this patch does so, reusing the "char_span" class that I introduced
in r250187 (as part of the fix for PR c/81405).

The patch also adds assertions to all access to the char_span.

gcc/c-family/ChangeLog:
	* c-format.c (get_corrected_substring): Update for
	location_get_source_line returning a char_span.  Use a char_span
	when handling the prefix of the correction.
	* c-indentation.c (get_visual_column): Update for
	location_get_source_line returning a char_span.
	(get_first_nws_vis_column): Likewise.

gcc/ChangeLog:
	* diagnostic-show-locus.c (layout::layout): Update for
	location_get_source_line returning a char_span.
	(struct char_span): Move to input.h.
	(struct correction): Update for fields in char_span becoming
	private.
	(struct source_line): Update for location_get_source_line
	returning a char_span.
	(layout::print_line): Likewise.
	* edit-context.c (edited_file::print_content): Likewise.
	(edited_file::print_diff_hunk): Likewise.
	(edited_file::print_run_of_changed_lines): Likewise.
	(edited_file::get_num_lines): Likewise.
	(edited_line::edited_line): Likewise.
	* final.c (asm_show_source): Likewise.
	* input.c (location_get_source_line): Convert return type
	from const char * to char_span, losing the final "line_len"
	param.
	(dump_location_info): Update for the above.
	(get_substring_ranges_for_loc): Likewise.  Use a char_span
	when handling the literal within the line.
	(test_reading_source_line): Update for location_get_source_line
	returning a char_span.
	* input.h (class char_span): Move here from
	diagnostic-show-locus.c, converting from a struct to a class.
	Make data members private.
	(char_span::operator bool): New.
	(char_span::length): New.
	(char_span::get_buffer): New.
	(char_span::operator[]): New.
	(char_span::subspan): Make const.
	(char_span::xstrdup): New.
	(location_get_source_line): Convert return type from const char *
	to char_span, losing the final "line_size" param.

gcc/testsuite/ChangeLog:
	* gcc.dg/plugin/diagnostic_plugin_test_show_locus.c
	(test_show_locus): Update for location_get_source_line returning a
	char_span.  Use char_span for handling words in the
	"test_many_nested_locations" fix-it example.

From-SVN: r259768

1 files changed, 46 insertions, 2 deletions

diff --git a/gcc/input.h b/gcc/input.h
index cec922f9c8d..4619663519a 100644
--- a/gcc/input.h
+++ b/gcc/input.h
@@ -38,8 +38,52 @@ STATIC_ASSERT (BUILTINS_LOCATION < RESERVED_LOCATION_COUNT);
 
 extern bool is_location_from_builtin_token (source_location);
 extern expanded_location expand_location (source_location);
-extern const char *location_get_source_line (const char *file_path, int line,
-					     int *line_size);
+
+/* A class capturing the bounds of a buffer, to allow for run-time
+   bounds-checking in a checked build.  */
+
+class char_span
+{
+ public:
+  char_span (const char *ptr, size_t n_elts) : m_ptr (ptr), m_n_elts (n_elts) {}
+
+  /* Test for a non-NULL pointer.  */
+  operator bool() const { return m_ptr; }
+
+  /* Get length, not including any 0-terminator (which may not be,
+     in fact, present).  */
+  size_t length () const { return m_n_elts; }
+
+  const char *get_buffer () const { return m_ptr; }
+
+  char operator[] (int idx) const
+  {
+    gcc_assert (idx >= 0);
+    gcc_assert ((size_t)idx < m_n_elts);
+    return m_ptr[idx];
+  }
+
+  char_span subspan (int offset, int n_elts) const
+  {
+    gcc_assert (offset >= 0);
+    gcc_assert (offset < (int)m_n_elts);
+    gcc_assert (n_elts >= 0);
+    gcc_assert (offset + n_elts <= (int)m_n_elts);
+    return char_span (m_ptr + offset, n_elts);
+  }
+
+  char *xstrdup () const
+  {
+    return ::xstrndup (m_ptr, m_n_elts);
+  }
+
+ private:
+  const char *m_ptr;
+  size_t m_n_elts;
+};
+
+extern char_span location_get_source_line (const char *file_path, int line);
+
 extern bool location_missing_trailing_newline (const char *file_path);
 extern expanded_location expand_location_to_spelling_point (source_location);
 extern source_location expansion_point_location_if_in_system_header (source_location);