[RFC, PATCH] Display inlining context for uninitialized warnings

[Vladislav Ivanishin <vlad at ispras dot ru>]

Hi, 

This patch (partially) adds displaying inlining context for
-W{maybe,}uninitialized warnings.  This is not as trivial to enable as
simply supplying the "%G" format specifier, so I have some questions
below.

I need this hunk 

 void
 percent_K_format (text_info *text, location_t loc, tree block)
 {
-  text->set_location (0, loc, SHOW_RANGE_WITH_CARET);
+  if (loc != UNKNOWN_LOCATION)
+    text->set_location (0, loc, SHOW_RANGE_WITH_CARET);
  
for two reasons:

- The gimple return stmt has UNKNOWN_LOCATION due to this code in
  lower_gimple_return ():

  if (gimple_return_retval (stmt) == gimple_return_retval (tmp_rs.stmt))
    {
      /* Remove the line number from the representative return statement.
         It now fills in for many such returns.  Failure to remove this
         will result in incorrect results for coverage analysis.  */
      gimple_set_location (tmp_rs.stmt, UNKNOWN_LOCATION);

  (In case you are wondering, the code and the comment were
  added in 2004.)

- When percent_K_format is called, TEXT might already hold precise
  location information in case its (indirect) caller is
  warning_at/error_at.  So it seems to me, this function lacks
  distinguishing the two cases: being called from plain warning/error
  functions vs. their *_at counterparts (the location shouldn't be
  updated in the latter case).

  Martin, you did the necessary work for percent_G_format to accept
  arbitrary gimple statements rather than just calls for PR86650, but
  left the PR open.  Do you remember running into that sort of problem,
  or was it something else?
  
Sometimes inlining context is still lost (with the current patch), as
can be seen e.g. with a version of the test with 's/unsigned yo/int yo/'
substitution applied.  (The chain of block = BLOCK_SUPERCONTEXT (block)
is broken - it ends with 0 rather than a FUNCTION_DECL.)  Is this known
and expected (e.g. because pass_late_warn_uninitialized runs very late),
or something to be investigated and fixed?

The patch was bootstrapped and regtested on x86_64-pc-linux-gnu.  Shall
it be applied?

        * tree-ssa-uninit.c (warn_uninit): Pass context (stmt of the uninit use)
        to warning_at.
        (warn_uninitialized_vars): Add %G format specifier.
        (warn_uninitialized_phi): Ditto.
        * tree-pretty-print.c (percent_K_format): Don't re-set location of TEXT
        to UNKNOWN_LOCATION.

testsuite/
        * gcc.dg/uninit-inlined.c: New test.
---
 gcc/testsuite/gcc.dg/uninit-inlined.c | 25 +++++++++++++++++++++++++
 gcc/tree-pretty-print.c               |  3 ++-
 gcc/tree-ssa-uninit.c                 |  8 ++++----
 3 files changed, 31 insertions(+), 5 deletions(-)
 create mode 100644 gcc/testsuite/gcc.dg/uninit-inlined.c

diff --git a/gcc/testsuite/gcc.dg/uninit-inlined.c b/gcc/testsuite/gcc.dg/uninit-inlined.c
new file mode 100644
index 00000000000..231a0b6b7c2
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/uninit-inlined.c
@@ -0,0 +1,25 @@
+/* { dg-do compile } */
+/* { dg-options "-O -Wmaybe-uninitialized" } */
+
+extern unsigned bar (int);
+
+extern int f;
+
+static int
+foo (int num)
+{
+  unsigned yo;
+  if (f)
+    yo = bar (num);
+  return yo; /* { dg-warning "may be used uninitialized" }  */
+}
+int
+test (int num)
+{
+  if (num == 42 || !num)
+    return foo (num);
+  return 0;
+}
+
+/* { dg-regexp "In function 'foo'," "In foo" } */
+/* { dg-regexp ".*inlined from 'test'.*" "Inilned from" } */
diff --git a/gcc/tree-pretty-print.c b/gcc/tree-pretty-print.c
index 329cc6fceeb..db1a00a6e49 100644
--- a/gcc/tree-pretty-print.c
+++ b/gcc/tree-pretty-print.c
@@ -4196,7 +4196,8 @@ newline_and_indent (pretty_printer *pp, int spc)
 void
 percent_K_format (text_info *text, location_t loc, tree block)
 {
-  text->set_location (0, loc, SHOW_RANGE_WITH_CARET);
+  if (loc != UNKNOWN_LOCATION)
+    text->set_location (0, loc, SHOW_RANGE_WITH_CARET);
   gcc_assert (pp_ti_abstract_origin (text) != NULL);
   *pp_ti_abstract_origin (text) = NULL;
 
diff --git a/gcc/tree-ssa-uninit.c b/gcc/tree-ssa-uninit.c
index fe8f8f0bc28..4d6f3773a87 100644
--- a/gcc/tree-ssa-uninit.c
+++ b/gcc/tree-ssa-uninit.c
@@ -179,7 +179,7 @@ warn_uninit (enum opt_code wc, tree t, tree expr, tree var,
   xloc = expand_location (location);
   floc = expand_location (cfun_loc);
   auto_diagnostic_group d;
-  if (warning_at (location, wc, gmsgid, expr))
+  if (warning_at (location, wc, gmsgid, context, expr))
     {
       TREE_NO_WARNING (expr) = 1;
 
@@ -257,12 +257,12 @@ warn_uninitialized_vars (bool warn_possibly_uninitialized)
 	      if (always_executed)
 		warn_uninit (OPT_Wuninitialized, use, SSA_NAME_VAR (use),
 			     SSA_NAME_VAR (use),
-			     "%qD is used uninitialized in this function", stmt,
+			     "%G%qD is used uninitialized in this function", stmt,
 			     UNKNOWN_LOCATION);
 	      else if (warn_possibly_uninitialized)
 		warn_uninit (OPT_Wmaybe_uninitialized, use, SSA_NAME_VAR (use),
 			     SSA_NAME_VAR (use),
-			     "%qD may be used uninitialized in this function",
+			     "%G%qD may be used uninitialized in this function",
 			     stmt, UNKNOWN_LOCATION);
 	    }
 
@@ -2615,7 +2615,7 @@ warn_uninitialized_phi (gphi *phi, vec<gphi *> *worklist,
     loc = UNKNOWN_LOCATION;
   warn_uninit (OPT_Wmaybe_uninitialized, uninit_op, SSA_NAME_VAR (uninit_op),
 	       SSA_NAME_VAR (uninit_op),
-	       "%qD may be used uninitialized in this function",
+	       "%G%qD may be used uninitialized in this function",
 	       uninit_use_stmt, loc);
 }
 
-- 
2.22.0

-- 
Vlad