json: preserve key-insertion order [PR109163]

PR other/109163 notes that when we write out JSON files, we traverse
the keys within each object via hash_map iteration, and thus the
ordering is non-deterministic - it can arbitrarily vary from run to
run and from different machines, making it harder for users to compare
results and determine if anything has "really" changed.

I'm running into this issue with SARIF output, but there are several
places where we're currently emitting JSON:

  * -fsave-optimization-record emits SRCFILE.opt-record.json.gz
	"This option is experimental and the format of the data within
	the compressed JSON file is subject to change."; see
	optinfo-emit-json.{h,cc}, dumpfile.cc, etc
  * -fdiagnostics-format= with the various "sarif" and "json" options
  * -fdump-analyzer-json is a developer option in the analyzer
  * gcov has:
     "-j, --json-format: Output JSON intermediate format into
     .gcov.json.gz file"

This patch adds an auto_vec to class json::object to preserve
key-insertion order, and use it when writing out objects.  Potentially
this slightly slows down JSON output, but I believe that this isn't
normally a bottleneck, and that the benefits to the user of
deterministic output are worth it.

I had first attempted to use ordered_hash_map.h for this, but ran into
impenetrable template errors, so this patch uses a simpler approach of
just adding an auto_vec to json::object.

Testing showed a failure of diagnostic-format-json-5.c, which was using
a convoluted set of regexps to consume the output; I believe that this
was brittle, and was intermittently failing for some of the random
orderings of output.  I rewrote these regexps to work with the expected
output order.  The other such tests seem to pass with the
now-deterministic orderings.

gcc/ChangeLog:
	PR other/109163
	* json.cc: Update comments to indicate that we now preserve
	insertion order of keys within objects.
	(object::print): Traverse keys in insertion order.
	(object::set): Preserve insertion order of keys.
	(selftest::test_writing_objects): Add an additional key to verify
	that we preserve insertion order.
	* json.h (object::m_keys): New field.

gcc/testsuite/ChangeLog:
	PR other/109163
	* c-c++-common/diagnostic-format-json-1.c: Update comment.
	* c-c++-common/diagnostic-format-json-2.c: Likewise.
	* c-c++-common/diagnostic-format-json-3.c: Likewise.
	* c-c++-common/diagnostic-format-json-4.c: Likewise.
	* c-c++-common/diagnostic-format-json-5.c: Rewrite regexps.
	* c-c++-common/diagnostic-format-json-stderr-1.c: Update comment.

Signed-off-by: David Malcolm <dmalcolm@redhat.com>
This commit is contained in:
David Malcolm 2023-03-24 11:38:14 -04:00
parent 0409aa5a2d
commit 7f1e15f743
8 changed files with 95 additions and 70 deletions

View file

@ -31,8 +31,11 @@ using namespace json;
/* class json::value. */
/* Dump this json::value tree to OUTF.
No formatting is done. There are no guarantees about the order
in which the key/value pairs of json::objects are printed. */
No formatting is done.
The key/value pairs of json::objects are printed in the order
in which the keys were originally inserted. */
void
value::dump (FILE *outf) const
@ -44,7 +47,7 @@ value::dump (FILE *outf) const
}
/* class json::object, a subclass of json::value, representing
an unordered collection of key/value pairs. */
an ordered collection of key/value pairs. */
/* json:object's dtor. */
@ -62,14 +65,17 @@ object::~object ()
void
object::print (pretty_printer *pp) const
{
/* Note that the order is not guaranteed. */
pp_character (pp, '{');
for (map_t::iterator it = m_map.begin (); it != m_map.end (); ++it)
/* Iterate in the order that the keys were inserted. */
unsigned i;
const char *key;
FOR_EACH_VEC_ELT (m_keys, i, key)
{
if (it != m_map.begin ())
if (i > 0)
pp_string (pp, ", ");
const char *key = const_cast <char *>((*it).first);
value *value = (*it).second;
map_t &mut_map = const_cast<map_t &> (m_map);
value *value = *mut_map.get (key);
pp_doublequote (pp);
pp_string (pp, key); // FIXME: escaping?
pp_doublequote (pp);
@ -97,9 +103,13 @@ object::set (const char *key, value *v)
*ptr = v;
}
else
/* If the key wasn't already present, take a copy of the key,
and store the value. */
m_map.put (xstrdup (key), v);
{
/* If the key wasn't already present, take a copy of the key,
and store the value. */
char *owned_key = xstrdup (key);
m_map.put (owned_key, v);
m_keys.safe_push (owned_key);
}
}
/* Get the json::value * for KEY.
@ -295,15 +305,17 @@ test_object_get ()
ASSERT_EQ (obj.get ("not-present"), NULL);
}
/* Verify that JSON objects are written correctly. We can't test more than
one key/value pair, as we don't impose a guaranteed ordering. */
/* Verify that JSON objects are written correctly. */
static void
test_writing_objects ()
{
object obj;
obj.set ("foo", new json::string ("bar"));
assert_print_eq (obj, "{\"foo\": \"bar\"}");
obj.set ("baz", new json::string ("quux"));
/* This test relies on json::object writing out key/value pairs
in key-insertion order. */
assert_print_eq (obj, "{\"foo\": \"bar\", \"baz\": \"quux\"}");
}
/* Verify that JSON arrays are written correctly. */

View file

@ -82,8 +82,11 @@ class value
void dump (FILE *) const;
};
/* Subclass of value for objects: an unordered collection of
key/value pairs. */
/* Subclass of value for objects: a collection of key/value pairs
preserving the ordering in which keys were inserted.
Preserving the order eliminates non-determinism in the output,
making it easier for the user to compare repeated invocations. */
class object : public value
{
@ -100,6 +103,9 @@ class object : public value
typedef hash_map <char *, value *,
simple_hashmap_traits<nofree_string_hash, value *> > map_t;
map_t m_map;
/* Keep track of order in which keys were inserted. */
auto_vec <const char *> m_keys;
};
/* Subclass of value for arrays. */

View file

@ -4,8 +4,7 @@
#error message
/* Use dg-regexp to consume the JSON output starting with
the innermost values, and working outwards.
We can't rely on any ordering of the keys. */
the innermost values, and working outwards. */
/* { dg-regexp "\"kind\": \"error\"" } */
/* { dg-regexp "\"column-origin\": 1" } */

View file

@ -4,8 +4,7 @@
#warning message
/* Use dg-regexp to consume the JSON output starting with
the innermost values, and working outwards.
We can't rely on any ordering of the keys. */
the innermost values, and working outwards. */
/* { dg-regexp "\"kind\": \"warning\"" } */
/* { dg-regexp "\"column-origin\": 1" } */

View file

@ -4,8 +4,7 @@
#warning message
/* Use dg-regexp to consume the JSON output starting with
the innermost values, and working outwards.
We can't rely on any ordering of the keys. */
the innermost values, and working outwards. */
/* { dg-regexp "\"kind\": \"error\"" } */
/* { dg-regexp "\"column-origin\": 1" } */

View file

@ -10,8 +10,7 @@ int test (void)
}
/* Use dg-regexp to consume the JSON output starting with
the innermost values, and working outwards.
We can't rely on any ordering of the keys. */
the innermost values, and working outwards. */
/* Verify nested diagnostics. */

View file

@ -8,49 +8,61 @@ int test (struct s *ptr)
return ptr->colour;
}
/* Use dg-regexp to consume the JSON output starting with
the innermost values, and working outwards.
We can't rely on any ordering of the keys. */
/* Verify fix-it hints.
/* { dg-regexp "\"kind\": \"error\"" } */
/* { dg-regexp "\"column-origin\": 1" } */
/* { dg-regexp "\"escape-source\": false" } */
/* { dg-regexp "\"message\": \".*\"" } */
Use dg-regexp to consume the JSON output from start to
finish, relying on the ordering of the keys.
The following uses indentation to visualize the structure
of the JSON (although the actual output is all on one line).
/* Verify fix-it hints. */
/* { dg-regexp "\"string\": \"color\"" } */
/* { dg-regexp "\"start\": \{" } */
/* { dg-regexp "\"file\": \"\[^\n\r\"\]*diagnostic-format-json-5.c\"" } */
/* { dg-regexp "\"line\": 8" } */
/* { dg-regexp "\"column\": 15" } */
/* { dg-regexp "\"display-column\": 15" } */
/* { dg-regexp "\"byte-column\": 15" } */
/* { dg-regexp "\"next\": \{" } */
/* { dg-regexp "\"file\": \"\[^\n\r\"\]*diagnostic-format-json-5.c\"" } */
/* { dg-regexp "\"line\": 8" } */
/* { dg-regexp "\"column\": 21" } */
/* { dg-regexp "\"display-column\": 21" } */
/* { dg-regexp "\"byte-column\": 21" } */
/* { dg-regexp "\"fixits\": \[\[\{\}, \]*\]" } */
/* { dg-regexp "\"caret\": \{" } */
/* { dg-regexp "\"file\": \"\[^\n\r\"\]*diagnostic-format-json-5.c\"" } */
/* { dg-regexp "\"line\": 8" } */
/* { dg-regexp "\"column\": 15" } */
/* { dg-regexp "\"display-column\": 15" } */
/* { dg-regexp "\"byte-column\": 15" } */
/* { dg-regexp "\"finish\": \{" } */
/* { dg-regexp "\"file\": \"\[^\n\r\"\]*diagnostic-format-json-5.c\"" } */
/* { dg-regexp "\"line\": 8" } */
/* { dg-regexp "\"column\": 20" } */
/* { dg-regexp "\"display-column\": 20" } */
/* { dg-regexp "\"byte-column\": 20" } */
/* { dg-regexp "\"locations\": \[\[\{\}, \]*\]" } */
/* { dg-regexp "\"children\": \[\[\]\[\]\]" } */
/* { dg-regexp "\[\[\{\}, \]*\]" } */
{ dg-regexp {\[} }
{ dg-regexp {\{} }
{ dg-regexp {"kind": "error"} }
{ dg-regexp {, "message": "'struct s' has no member named 'colour'; did you mean 'color'\?"} }
{ dg-regexp {, "children": \[\]} }
{ dg-regexp {, "column-origin": 1} }
{ dg-regexp {, "locations": } }
{ dg-regexp {\[} }
{ dg-regexp {\{} }
{ dg-regexp {"caret": } }
{ dg-regexp {\{} }
{ dg-regexp {"file": "[^\n\r"]*diagnostic-format-json-5.c"} }
{ dg-regexp {, "line": 8} }
{ dg-regexp {, "display-column": 15} }
{ dg-regexp {, "byte-column": 15} }
{ dg-regexp {, "column": 15} }
{ dg-regexp {\}} }
{ dg-regexp {, "finish": } }
{ dg-regexp {\{} }
{ dg-regexp {"file": "[^\n\r"]*diagnostic-format-json-5.c"} }
{ dg-regexp {, "line": 8} }
{ dg-regexp {, "display-column": 20} }
{ dg-regexp {, "byte-column": 20} }
{ dg-regexp {, "column": 20} }
{ dg-regexp {\}} }
{ dg-regexp {\}} }
{ dg-regexp {\]} }
{ dg-regexp {, "fixits": } }
{ dg-regexp {\[} }
{ dg-regexp {\{} }
{ dg-regexp {"start": } }
{ dg-regexp {\{} }
{ dg-regexp {"file": "[^\n\r"]*diagnostic-format-json-5.c"} }
{ dg-regexp {, "line": 8} }
{ dg-regexp {, "display-column": 15} }
{ dg-regexp {, "byte-column": 15} }
{ dg-regexp {, "column": 15} }
{ dg-regexp {\}} }
{ dg-regexp {, "next": } }
{ dg-regexp {\{} }
{ dg-regexp {"file": "[^\n\r"]*diagnostic-format-json-5.c"} }
{ dg-regexp {, "line": 8} }
{ dg-regexp {, "display-column": 21} }
{ dg-regexp {, "byte-column": 21} }
{ dg-regexp {, "column": 21} }
{ dg-regexp {\}} }
{ dg-regexp {, "string": "color"} }
{ dg-regexp {\}} }
{ dg-regexp {\]} }
{ dg-regexp {, "escape-source": false\}} }
{ dg-regexp {\]} } */

View file

@ -6,8 +6,7 @@
#error message
/* Use dg-regexp to consume the JSON output starting with
the innermost values, and working outwards.
We can't rely on any ordering of the keys. */
the innermost values, and working outwards. */
/* { dg-regexp "\"kind\": \"error\"" } */
/* { dg-regexp "\"column-origin\": 1" } */