[PATCH] C FE: fix range of primary-expression in c_parser_postfix_expression

[David Malcolm <dmalcolm at redhat dot com>]

In the C frontend,
  c_parser_postfix_expression
after parsing a primary expression passes "loc", the location of the
*first token* in that expression to
  c_parser_postfix_expression_after_primary,
which thus discards any range information we had for primary
expressions containing more than one token; we get just the range of
the first token.

An example of this can be seen in this testcase from:
  https://gcc.gnu.org/wiki/ClangDiagnosticsComparison

void foo(char **argP, char **argQ)
{
  (argP - argQ)();
  argP();
}

for which trunk currently gives these ranges:

diagnostic-range-bad-called-object.c:7:3: error: called object is not a function or function pointer
   (argP - argQ)();
   ^

diagnostic-range-bad-called-object.c:14:3: error: called object 'argP' is not a function or function pointer
   argP();
   ^~~~

The second happens to be correct, but the first is missing
range information.

The following patch is a one-liner to preserve the expression's location,
changing the first to:

diagnostic-range-bad-called-object.c:7:9: error: called object is not a function or function pointer
   (argP - argQ)();
   ~~~~~~^~~~~~~

and leaving the second unchanged.

Applying this fix requires tweaking some column numbers for expected
locations in gcc.dg/cast-function-1.c; the output of trunk was of the
form:

cast-function-1.c:21:7: warning: function called through a non-compatible type
   d = ((double (*) (int)) foo1) (i);
       ^

which the patch changes to:

cast-function-1.c:21:8: warning: function called through a non-compatible type
   d = ((double (*) (int)) foo1) (i);
       ~^~~~~~~~~~~~~~~~~~~~~~~~

which I feel is an improvement.

Successfully bootstrapped&regrtested on x86_64-pc-linux-gnu.
Adds 6 new PASS results to gcc.sum

OK for trunk in stage 3?

gcc/c/ChangeLog:
	* c-parser.c (c_parser_postfix_expression): Use EXPR_LOC_OR_LOC
	to preserve range information for the primary expression
	in the call to c_parser_postfix_expression_after_primary.

gcc/testsuite/ChangeLog:
	* gcc.dg/cast-function-1.c (bar): Update column numbers.
	* gcc.dg/diagnostic-range-bad-called-object.c: New test case.
---
 gcc/c/c-parser.c                                   |  3 ++-
 gcc/testsuite/gcc.dg/cast-function-1.c             |  8 ++++----
 .../gcc.dg/diagnostic-range-bad-called-object.c    | 24 ++++++++++++++++++++++
 3 files changed, 30 insertions(+), 5 deletions(-)
 create mode 100644 gcc/testsuite/gcc.dg/diagnostic-range-bad-called-object.c

diff --git a/gcc/c/c-parser.c b/gcc/c/c-parser.c
index 5c32f45..e149e19 100644
--- a/gcc/c/c-parser.c
+++ b/gcc/c/c-parser.c
@@ -7954,7 +7954,8 @@ c_parser_postfix_expression (c_parser *parser)
       expr.value = error_mark_node;
       break;
     }
-  return c_parser_postfix_expression_after_primary (parser, loc, expr);
+  return c_parser_postfix_expression_after_primary
+    (parser, EXPR_LOC_OR_LOC (expr.value, loc), expr);
 }
 
 /* Parse a postfix expression after a parenthesized type name: the
diff --git a/gcc/testsuite/gcc.dg/cast-function-1.c b/gcc/testsuite/gcc.dg/cast-function-1.c
index ab42db1..5228b55 100644
--- a/gcc/testsuite/gcc.dg/cast-function-1.c
+++ b/gcc/testsuite/gcc.dg/cast-function-1.c
@@ -18,14 +18,14 @@ typedef struct {
 
 void bar(double d, int i, str_t s)
 {
-  d = ((double (*) (int)) foo1) (i);  /* { dg-warning "7:non-compatible|abort" } */
-  i = ((int (*) (double)) foo1) (d);  /* { dg-warning "7:non-compatible|abort" } */
-  s = ((str_t (*) (int)) foo1) (i);   /* { dg-warning "7:non-compatible|abort" } */
+  d = ((double (*) (int)) foo1) (i);  /* { dg-warning "8:non-compatible|abort" } */
+  i = ((int (*) (double)) foo1) (d);  /* { dg-warning "8:non-compatible|abort" } */
+  s = ((str_t (*) (int)) foo1) (i);   /* { dg-warning "8:non-compatible|abort" } */
   ((void (*) (int)) foo1) (d);        /* { dg-warning "non-compatible|abort" } */
   i = ((int (*) (int)) foo1) (i);     /* { dg-bogus "non-compatible|abort" } */
   (void) foo1 (i);                    /* { dg-bogus "non-compatible|abort" } */
 
-  d = ((double (*) (int)) foo2) (i);  /* { dg-warning "7:non-compatible|abort" } */
+  d = ((double (*) (int)) foo2) (i);  /* { dg-warning "8:non-compatible|abort" } */
   i = ((int (*) (double)) foo2) (d);  /* { dg-bogus "non-compatible|abort" } */
   s = ((str_t (*) (int)) foo2) (i);   /* { dg-warning "non-compatible|abort" } */
   ((void (*) (int)) foo2) (d);        /* { dg-warning "non-compatible|abort" } */
diff --git a/gcc/testsuite/gcc.dg/diagnostic-range-bad-called-object.c b/gcc/testsuite/gcc.dg/diagnostic-range-bad-called-object.c
new file mode 100644
index 0000000..95fb3e9
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/diagnostic-range-bad-called-object.c
@@ -0,0 +1,24 @@
+/* { dg-options "-fdiagnostics-show-caret" } */
+
+/* Adapted from https://gcc.gnu.org/wiki/ClangDiagnosticsComparison */
+
+void call_of_non_function_ptr (char **argP, char **argQ)
+{
+  (argP - argQ)(); /* { dg-error "called object is not a function or function pointer" } */
+
+/* { dg-begin-multiline-output "" }
+   (argP - argQ)();
+   ~~~~~~^~~~~~~
+   { dg-end-multiline-output "" } */
+
+  argP();       /* { dg-error "called object 'argP' is not a function or function pointer" } */
+
+/* { dg-begin-multiline-output "" }
+   argP();
+   ^~~~
+   { dg-end-multiline-output "" }
+   { dg-begin-multiline-output "" }
+ void call_of_non_function_ptr (char **argP, char **argQ)
+                                       ^~~~
+   { dg-end-multiline-output "" } */
+}
-- 
1.8.5.3