diagnostics: sort symbols per location

Because the checking of the grammar is made by phases after the whole
grammar was read, we sometimes have diagnostics that look weird.  In
some case, within one type of checking, the entities are not checked
in the order in which they appear in the file.  For instance, checking
symbols is done on the list of symbols sorted by tag:

    foo.y:1.20-22: warning: symbol BAR is used, but is not defined as a token and has no rules [-Wother]
        1 | %destructor {} QUX BAR
          |                    ^~~
    foo.y:1.16-18: warning: symbol QUX is used, but is not defined as a token and has no rules [-Wother]
        1 | %destructor {} QUX BAR
          |                ^~~

Let's sort them by location instead:

    foo.y:1.16-18: warning: symbol 'QUX' is used, but is not defined as a token and has no rules [-Wother]
        1 | %destructor {} QUX BAR
          |                ^~~
    foo.y:1.20-22: warning: symbol 'BAR' is used, but is not defined as a token and has no rules [-Wother]
        1 | %destructor {} QUX BAR
          |                    ^~~

* src/location.h (location_cmp): Be robust to empty file names.
* src/symtab.c (symbol_cmp): Sort by location.
* tests/input.at: Adjust expectations.

src/location.h

@@ -71,7 +71,12 @@ boundary_set (boundary *p, const char *f, int l, int c, int b)
 static inline int
 boundary_cmp (boundary a, boundary b)
 {
-  int res = strcmp (a.file, b.file);
+  /* Locations with no file first.  */
+  int res =
+    a.file && b.file ? strcmp (a.file, b.file)
+    : a.file ? 1
+    : b.file ? -1
+    : 0;
   if (!res)
     res = a.line - b.line;
   if (!res)

src/symtab.c

@@ -925,8 +925,8 @@ symbols_free (void)
 static int
 symbol_cmp (void const *a, void const *b)
 {
-  return strcmp ((*(symbol * const *)a)->tag,
-                 (*(symbol * const *)b)->tag);
+  return location_cmp ((*(symbol * const *)a)->location,
+                       (*(symbol * const *)b)->location);
 }
 
 /* Store in *SORTED an array of pointers to the symbols contained in
@@ -952,14 +952,13 @@ void
 symbols_check_defined (void)
 {
   table_sort (symbol_table, &symbols_sorted);
-  /* semantic_type, like symbol, starts with a 'tag' field.  And here
-     we only deal with arrays/hashes of pointers, sizeof is not an
-     issue.
+  /* semantic_type, like symbol, starts with a 'tag' field and then a
+     'location' field.  And here we only deal with arrays/hashes of
+     pointers, sizeof is not an issue.
 
      So instead of implementing table_sort (and symbol_cmp) once for
      each type, let's lie a bit to the typing system, and treat
-     'semantic_type' as if it were 'symbol'.  Anyway this is only
-     about arrays of pointers.  */
+     'semantic_type' as if it were 'symbol'. */
   table_sort (semantic_type_table, (symbol ***) &semantic_types_sorted);
 
   for (int i = 0; symbols_sorted[i]; ++i)
@@ -1019,7 +1018,7 @@ symbols_token_translations_init (void)
   for (int i = 0; i < max_user_token_number + 1; ++i)
     token_translations[i] = undeftoken->content->number;
   for (int i = 0; symbols_sorted[i]; ++i)
-    symbol_translation(symbols_sorted[i]);
+    symbol_translation (symbols_sorted[i]);
 }
 
 
@@ -1033,7 +1032,7 @@ symbols_pack (void)
 {
   symbols = xcalloc (nsyms, sizeof *symbols);
   for (int i = 0; symbols_sorted[i]; ++i)
-    symbol_pack(symbols_sorted[i]);
+    symbol_pack (symbols_sorted[i]);
 
   /* Aliases leave empty slots in symbols, so remove them.  */
   {

tests/diagnostics.at

@@ -427,16 +427,16 @@ res: QUX baz
 [[%%
 res: QUX baz
 bar: QUUX
-]],
-[1],
-[[input.y:11.6-9: <error>error:</error> symbol 'QUUX' is used, but is not defined as a token and has no rules
-   11 | bar: <error>QUUX</error>
+]],
 [1],
 [[input.y:10.6-8: <error>error:</error> symbol 'QUX' is used, but is not defined as a token and has no rules
    10 | res: <error>QUX</error> baz
       |      <error>^~~</error>
 input.y:10.10-12: <error>error:</error> symbol 'baz' is used, but is not defined as a token and has no rules; did you mean 'bar'?
    10 | res: QUX <error>baz</error>
+      |          <error>^~~</error>
+      |          <fixit-insert>bar</fixit-insert>
+input.y:11.6-9: <error>error:</error> symbol 'QUUX' is used, but is not defined as a token and has no rules
    11 | bar: <error>QUUX</error>
       |      <error>^~~~</error>
 ]])

tests/input.at

@@ -822,15 +822,15 @@ exp: bar;
 ]])
 
 AT_BISON_CHECK([-fcaret input.y], [1], [],
-[[input.y:2.16-18: error: symbol 'bar' is used, but is not defined as a token and has no rules
-    2 | %destructor {} bar
-      |                ^~~
+[[input.y:1.13-15: warning: symbol 'foo' is used, but is not defined as a token and has no rules [-Wother]
+    1 | %printer {} foo baz
+      |             ^~~
 input.y:1.17-19: warning: symbol 'baz' is used, but is not defined as a token and has no rules [-Wother]
     1 | %printer {} foo baz
       |                 ^~~
-input.y:1.13-15: warning: symbol 'foo' is used, but is not defined as a token and has no rules [-Wother]
-    1 | %printer {} foo baz
-      |             ^~~
+input.y:2.16-18: error: symbol 'bar' is used, but is not defined as a token and has no rules
+    2 | %destructor {} bar
+      |                ^~~
 input.y:3.13-15: warning: symbol 'qux' is used, but is not defined as a token and has no rules [-Wother]
     3 | %type <foo> qux
       |             ^~~
@@ -1061,9 +1061,9 @@ AT_BISON_CHECK([-fcaret input.y], [1], [],
 input.y:2.10-12: error: user token number 42 redeclaration for BAR
     2 |          BAR 42 "foo"
       |          ^~~
-input.y:1.8-10:      previous declaration for FOO
+input.y:1.15-19:     previous declaration for "foo"
     1 | %token FOO 42 "foo"
-      |        ^~~
+      |               ^~~~~
 ]])
 
 AT_CLEANUP