[PATCH 2/6] gdbsupport/selftest: print expression when selftest fails and re-format

[Simon Marchi <simon.marchi@efficios.com>]

This is a small step towards printing rich error messages when selftests
fail.  Add a selftests::failed_selftest function, called by SELF_CHECK
when the check fails.  It formats the error message, which now includes
the text of the failed expression (passed as a string from the
SELF_CHECK macro), and throws an error with the new error code
SELF_CHECK_FAILED_ERROR.  Change the output to a single line starting
with "FAIL:", followed by the location and the expression.

The SELF_CHECK_FAILED_ERROR error code allows the selftest runner to tell a
failed SELF_CHECK apart from other errors thrown during a test, and report
them differently.

This changes the output when there are failed selftests from:

    $ ./gdb -nx -q --data-directory=data-directory -ex "maint selftest string_" -batch
    Running selftest string_appendf.
    Running selftest string_printf.
    Self test failed: self-test failed at /home/smarchi/src/binutils-gdb/gdb/unittests/common-utils-selftests.c:35
    Running selftest string_vappendf.
    Running selftest string_vprintf.
    Self test failed: self-test failed at /home/smarchi/src/binutils-gdb/gdb/unittests/common-utils-selftests.c:35

    Failures:
      string_printf
      string_vprintf

    Ran 4 unit tests, 2 failed

to:

    $ ./gdb -nx -q --data-directory=data-directory -ex "maint selftest string_" -batch
    Running selftest string_appendf.
    Running selftest string_printf.
    FAIL: /home/smarchi/src/binutils-gdb/gdb/unittests/common-utils-selftests.c:35: func ("%s", "test") == "test boo"
    Running selftest string_vappendf.
    Running selftest string_vprintf.
    FAIL: /home/smarchi/src/binutils-gdb/gdb/unittests/common-utils-selftests.c:35: func ("%s", "test") == "test boo"

    Failures:
      string_printf
      string_vprintf

    Ran 4 unit tests, 2 failed

Other errors thrown during a selftest, which used to be printed as:

    Self test failed: oh no

are now printed as:

    FAIL: unexpected exception: oh no

The output looks similar with gdbserver (the formatting code is shared,
so it's expected).

I wish we could add some colors, but since this code is in gdbsupport,
it's not straightforward.  Maybe we can add that later.

Change-Id: Ice0c930add2dc0d2395806cc17f9d2dc247db419
---
 gdbsupport/common-exceptions.h |  3 +++
 gdbsupport/selftest.cc         | 15 ++++++++++++++-
 gdbsupport/selftest.h          | 17 +++++++++++++----
 3 files changed, 30 insertions(+), 5 deletions(-)

diff --git a/gdbsupport/common-exceptions.h b/gdbsupport/common-exceptions.h
index 058260b5f270..1b3de6a2f955 100644
--- a/gdbsupport/common-exceptions.h
+++ b/gdbsupport/common-exceptions.h
@@ -112,6 +112,9 @@ enum errors {
      "_ERROR" is appended to the name.  */
   MAX_COMPLETIONS_REACHED_ERROR,
 
+  /* A SELF_CHECK failed during a selftest.  */
+  SELF_CHECK_FAILED_ERROR,
+
   /* Add more errors here.  */
   NR_ERRORS
 };
diff --git a/gdbsupport/selftest.cc b/gdbsupport/selftest.cc
index 611bb990a0e2..85eee59e3c4b 100644
--- a/gdbsupport/selftest.cc
+++ b/gdbsupport/selftest.cc
@@ -101,7 +101,11 @@ run_tests (gdb::array_view<const char *const> filters, bool verbose)
 	}
       catch (const gdb_exception_error &ex)
 	{
-	  debug_printf ("Self test failed: %s\n", ex.what ());
+	  if (ex.error == SELF_CHECK_FAILED_ERROR)
+	    debug_printf ("FAIL: %s\n", ex.what ());
+	  else
+	    debug_printf ("FAIL: unexpected exception: %s\n", ex.what ());
+
 	  failed.push_back (test.name.c_str ());
 	}
 
@@ -138,4 +142,13 @@ all_selftests ()
   return selftests_range (tests.cbegin (), tests.cend ());
 }
 
+/* See selftest.h.  */
+
+void
+failed_selftest (const char *file, int line, const char *expression)
+{
+  throw_error (SELF_CHECK_FAILED_ERROR, "%s:%d: %s", file, line,
+	       expression);
+}
+
 } /* namespace selftests */
diff --git a/gdbsupport/selftest.h b/gdbsupport/selftest.h
index 2a1539827940..ddf925dd3524 100644
--- a/gdbsupport/selftest.h
+++ b/gdbsupport/selftest.h
@@ -83,14 +83,23 @@ extern void run_tests (gdb::array_view<const char *const> filters,
 
 /* Reset GDB or GDBserver's internal state.  */
 extern void reset ();
+
+/* Function called by macro SELF_CHECK when a selftest fails.  Throw an
+   error with code SELF_CHECK_FAILED_ERROR describing the failure.  */
+
+[[noreturn]] void failed_selftest (const char *file, int line,
+				   const char *expression);
+
 }
 
 /* Check that VALUE is true, and, if not, throw an exception.  */
 
 #define SELF_CHECK(VALUE)						\
-  do {									\
-    if (!(VALUE))							\
-      error (_("self-test failed at %s:%d"), __FILE__, __LINE__);	\
-  } while (0)
+  do									\
+    {									\
+      if (!(VALUE))							\
+	selftests::failed_selftest (__FILE__, __LINE__, #VALUE);	\
+    }									\
+  while (0)
 
 #endif /* GDBSUPPORT_SELFTEST_H */
-- 
2.56.0