Fix memory leak of pretty_printer prefixes

We were rather sloppy about handling the ownership of prefixes for
pretty_printer, and this lead to a memory leak for any time a
diagnostic_show_locus call emits multiple line spans.

This showed up in "make selftest-valgrind" as:

3,976 bytes in 28 blocks are definitely lost in loss record 632 of 669
   at 0x4A0645D: malloc (in /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)
   by 0x1F08227: xmalloc (xmalloc.c:147)
   by 0x1F083E6: xvasprintf (xvasprintf.c:58)
   by 0x1E7EC7D: build_message_string(char const*, ...) (diagnostic.c:78)
   by 0x1E7F438: diagnostic_get_location_text(diagnostic_context*, expanded_location) (diagnostic.c:328)
   by 0x1E7FD54: default_diagnostic_start_span_fn(diagnostic_context*, expanded_location) (diagnostic.c:626)
   by 0x1EB3508: selftest::test_diagnostic_context::start_span_cb(diagnostic_context*, expanded_location) (selftest-diagnostic.c:57)
   by 0x1E89215: diagnostic_show_locus(diagnostic_context*, rich_location*, diagnostic_t) (diagnostic-show-locus.c:1992)
   by 0x1E8ECAD: selftest::test_fixit_insert_containing_newline_2(selftest::line_table_case const&) (diagnostic-show-locus.c:3044)
   by 0x1EB0606: selftest::for_each_line_table_case(void (*)(selftest::line_table_case const&)) (input.c:3525)
   by 0x1E8F3F5: selftest::diagnostic_show_locus_c_tests() (diagnostic-show-locus.c:3164)
   by 0x1E010BF: selftest::run_tests() (selftest-run-tests.c:88)

4,004 bytes in 28 blocks are definitely lost in loss record 633 of 669
   at 0x4A0645D: malloc (in /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)
   by 0x1F08227: xmalloc (xmalloc.c:147)
   by 0x1F083E6: xvasprintf (xvasprintf.c:58)
   by 0x1E7EC7D: build_message_string(char const*, ...) (diagnostic.c:78)
   by 0x1E7F438: diagnostic_get_location_text(diagnostic_context*, expanded_location) (diagnostic.c:328)
   by 0x1E7FD54: default_diagnostic_start_span_fn(diagnostic_context*, expanded_location) (diagnostic.c:626)
   by 0x1EB3508: selftest::test_diagnostic_context::start_span_cb(diagnostic_context*, expanded_location) (selftest-diagnostic.c:57)
   by 0x1E89215: diagnostic_show_locus(diagnostic_context*, rich_location*, diagnostic_t) (diagnostic-show-locus.c:1992)
   by 0x1E8B373: selftest::test_diagnostic_show_locus_fixit_lines(selftest::line_table_case const&) (diagnostic-show-locus.c:2500)
   by 0x1EB0606: selftest::for_each_line_table_case(void (*)(selftest::line_table_case const&)) (input.c:3525)
   by 0x1E8F3B9: selftest::diagnostic_show_locus_c_tests() (diagnostic-show-locus.c:3159)
   by 0x1E010BF: selftest::run_tests() (selftest-run-tests.c:88)

This patch fixes the leaks by ensuring that the pretty_printer "owns"
the prefix if it's non-NULL, freeing it in the dtor and in pp_set_prefix.

gcc/cp/ChangeLog:
	* error.c (cxx_print_error_function): Duplicate "file" before
	passing it to pp_set_prefix.
	(cp_print_error_function): Use pp_take_prefix when saving the
	existing prefix.

gcc/ChangeLog:
	* diagnostic-show-locus.c (diagnostic_show_locus): Use
	pp_take_prefix when saving the existing prefix.
	* diagnostic.c (diagnostic_append_note): Likewise.
	* langhooks.c (lhd_print_error_function): Likewise.
	* pretty-print.c (pp_set_prefix): Drop the "const" from "prefix"
	param's type.  Free the existing prefix.
	(pp_take_prefix): New function.
	(pretty_printer::pretty_printer): Drop the prefix parameter.
	Rename the length parameter to match the comment.
	(pretty_printer::~pretty_printer): Free the prefix.
	* pretty-print.h (pretty_printer::pretty_printer): Drop the prefix
	parameter.
	(struct pretty_printer): Drop the "const" from "prefix" field's
	type and clarify memory management.
	(pp_set_prefix): Drop the "const" from the 2nd param.
	(pp_take_prefix): New decl.

From-SVN: r263275

1 files changed, 23 insertions, 8 deletions

diff --git a/gcc/pretty-print.c b/gcc/pretty-print.c
index dc7791a..736af8f 100644
--- a/gcc/pretty-print.c
+++ b/gcc/pretty-print.c
@@ -1482,23 +1482,38 @@ pp_clear_output_area (pretty_printer *pp)
   pp_buffer (pp)->line_length = 0;
 }
 
-/* Set PREFIX for PRETTY-PRINTER.  */
+/* Set PREFIX for PRETTY-PRINTER, taking ownership of PREFIX, which
+   will eventually be free-ed.  */
+
 void
-pp_set_prefix (pretty_printer *pp, const char *prefix)
+pp_set_prefix (pretty_printer *pp, char *prefix)
 {
+  free (pp->prefix);
   pp->prefix = prefix;
   pp_set_real_maximum_length (pp);
   pp->emitted_prefix = false;
   pp_indentation (pp) = 0;
 }
 
+/* Take ownership of PP's prefix, setting it to NULL.
+   This allows clients to save, overide, and then restore an existing
+   prefix, without it being free-ed.  */
+
+char *
+pp_take_prefix (pretty_printer *pp)
+{
+  char *result = pp->prefix;
+  pp->prefix = NULL;
+  return result;
+}
+
 /* Free PRETTY-PRINTER's prefix, a previously malloc()'d string.  */
 void
 pp_destroy_prefix (pretty_printer *pp)
 {
   if (pp->prefix != NULL)
     {
-      free (CONST_CAST (char *, pp->prefix));
+      free (pp->prefix);
       pp->prefix = NULL;
     }
 }
@@ -1535,10 +1550,9 @@ pp_emit_prefix (pretty_printer *pp)
     }
 }
 
-/* Construct a PRETTY-PRINTER with PREFIX and of MAXIMUM_LENGTH
-   characters per line.  */
+/* Construct a PRETTY-PRINTER of MAXIMUM_LENGTH characters per line.  */
 
-pretty_printer::pretty_printer (const char *p, int l)
+pretty_printer::pretty_printer (int maximum_length)
   : buffer (new (XCNEW (output_buffer)) output_buffer ()),
     prefix (),
     padding (pp_none),
@@ -1552,10 +1566,10 @@ pretty_printer::pretty_printer (const char *p, int l)
     translate_identifiers (true),
     show_color ()
 {
-  pp_line_cutoff (this) = l;
+  pp_line_cutoff (this) = maximum_length;
   /* By default, we emit prefixes once per message.  */
   pp_prefixing_rule (this) = DIAGNOSTICS_SHOW_PREFIX_ONCE;
-  pp_set_prefix (this, p);
+  pp_set_prefix (this, NULL);
 }
 
 pretty_printer::~pretty_printer ()
@@ -1564,6 +1578,7 @@ pretty_printer::~pretty_printer ()
     delete m_format_postprocessor;
   buffer->~output_buffer ();
   XDELETE (buffer);
+  free (prefix);
 }
 
 /* Append a string delimited by START and END to the output area of