[PATCH] PR jit/63969: Fix segfault in error-handling when driver isn't found

[David Malcolm <dmalcolm at redhat dot com>]

It's not clear to me if I can approve my own patches to the jit, so
here's a fix for PR 63969.

Tested via "make check-jit" on Fedora 20 x86_64; testcase segfaults
without the fix to jit-playback.c and is fixed with it; all other
testcases continue to pass.

OK for trunk?


>From 0901383f1a1ad296b939687298b8321446bc54e3 Mon Sep 17 00:00:00 2001
From: David Malcolm <dmalcolm@redhat.com>
Date: Thu, 20 Nov 2014 01:06:14 -0500
Subject: [PATCH] PR jit/63969: Fix segfault in error-handling when driver
 isn't found

If the driver isn't found on the path, pex_one attempts to print an
error message, but if GCC_JIT_STR_OPTION_PROGNAME wasn't set,
pex_one's pname was NULL, leading to a segfault.

Ensure that pex_one is called with a non-NULL pname, and add a testcase
to verify that the user gets a sane error message if the driver isn't on
PATH.

gcc/jit/ChangeLog:
	* jit-playback.c: Ensure that ctxt_progname is non-NULL.

gcc/testsuite/ChangeLog:
	* jit.dg/harness.h (CHECK_STRING_STARTS_WITH): New.
	(check_string_starts_with): New.
	* jit.dg/test-error-pr63969-missing-driver.c: New.
---
 gcc/jit/jit-playback.c                             |  9 +++--
 gcc/testsuite/jit.dg/harness.h                     | 31 ++++++++++++++++++
 .../jit.dg/test-error-pr63969-missing-driver.c     | 38 ++++++++++++++++++++++
 3 files changed, 76 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/jit.dg/test-error-pr63969-missing-driver.c

diff --git a/gcc/jit/jit-playback.c b/gcc/jit/jit-playback.c
index 8fdfa29..584a8e6 100644
--- a/gcc/jit/jit-playback.c
+++ b/gcc/jit/jit-playback.c
@@ -1571,9 +1571,11 @@ compile ()
   /* Pass in user-provided program name as argv0, if any, so that it
      makes it into GCC's "progname" global, used in various diagnostics. */
   ctxt_progname = get_str_option (GCC_JIT_STR_OPTION_PROGNAME);
-  fake_args[0] =
-    (ctxt_progname ? ctxt_progname : "libgccjit.so");
 
+  if (!ctxt_progname)
+    ctxt_progname = "libgccjit.so";
+
+  fake_args[0] = ctxt_progname;
   fake_args[1] = m_path_c_file;
   num_args = 2;
 
@@ -1689,6 +1691,9 @@ compile ()
     /* pex argv arrays are NULL-terminated.  */
     argv[6] = NULL;
 
+    /* pex_one's error-handling requires pname to be non-NULL.  */
+    gcc_assert (ctxt_progname);
+
     errmsg = pex_one (PEX_SEARCH, /* int flags, */
 		      gcc_driver_name,
 		      const_cast<char * const *> (argv),
diff --git a/gcc/testsuite/jit.dg/harness.h b/gcc/testsuite/jit.dg/harness.h
index f326891..bff64de 100644
--- a/gcc/testsuite/jit.dg/harness.h
+++ b/gcc/testsuite/jit.dg/harness.h
@@ -81,6 +81,9 @@ static char test[1024];
 #define CHECK_STRING_VALUE(ACTUAL, EXPECTED) \
   check_string_value ((ACTUAL), (EXPECTED));
 
+#define CHECK_STRING_STARTS_WITH(ACTUAL, EXPECTED_PREFIX) \
+  check_string_starts_with ((ACTUAL), (EXPECTED_PREFIX));
+
 #define CHECK(COND) \
   do {					\
     if (COND)				\
@@ -103,6 +106,10 @@ verify_code (gcc_jit_context *ctxt, gcc_jit_result *result);
 
 extern void check_string_value (const char *actual, const char *expected);
 
+extern void
+check_string_starts_with (const char *actual,
+			  const char *expected_prefix);
+
 /* Implement framework needed for turning the testcase hooks into an
    executable.  test-combination.c and test-threads.c each combine multiple
    testcases into larger testcases, so we have COMBINED_TEST as a way of
@@ -137,6 +144,30 @@ void check_string_value (const char *actual, const char *expected)
       pass ("%s: actual: NULL == expected: NULL");
 }
 
+void
+check_string_starts_with (const char *actual,
+			  const char *expected_prefix)
+{
+  if (!actual)
+    {
+      fail ("%s: actual: NULL != expected prefix: \"%s\"",
+	    test, expected_prefix);
+      fprintf (stderr, "incorrect value\n");
+      abort ();
+    }
+
+  if (strncmp (actual, expected_prefix, strlen (expected_prefix)))
+    {
+      fail ("%s: actual: \"%s\" did not begin with expected prefix: \"%s\"",
+	    test, actual, expected_prefix);
+      fprintf (stderr, "incorrect value\n");
+      abort ();
+    }
+
+  pass ("%s: actual: \"%s\" begins with expected prefix: \"%s\"",
+	test, actual, expected_prefix);
+}
+
 static void set_options (gcc_jit_context *ctxt, const char *argv0)
 {
   /* Set up options.  */
diff --git a/gcc/testsuite/jit.dg/test-error-pr63969-missing-driver.c b/gcc/testsuite/jit.dg/test-error-pr63969-missing-driver.c
new file mode 100644
index 0000000..13f5e3b
--- /dev/null
+++ b/gcc/testsuite/jit.dg/test-error-pr63969-missing-driver.c
@@ -0,0 +1,38 @@
+/* PR jit/63969: libgccjit would segfault inside gcc_jit_context_compile
+   if the driver wasn't found on PATH if GCC_JIT_STR_OPTION_PROGNAME was
+   NULL.  */
+
+#include <stdlib.h>
+#include <stdio.h>
+
+#include "libgccjit.h"
+
+#include "harness.h"
+
+void
+create_code (gcc_jit_context *ctxt, void *user_data)
+{
+  /* Create nothing within the context.  */
+
+  /* harness.h's set_options has set a sane value for
+     GCC_JIT_STR_OPTION_PROGNAME, but PR jit/63969 only segfaulted if it's
+     NULL.
+
+     Unset it.  */
+  gcc_jit_context_set_str_option (ctxt, GCC_JIT_STR_OPTION_PROGNAME, NULL);
+
+  /* Break PATH, so that the driver can't be found
+     by gcc::jit::playback::context::compile ()
+     within gcc_jit_context_compile.  */
+  unsetenv ("PATH");
+}
+
+void
+verify_code (gcc_jit_context *ctxt, gcc_jit_result *result)
+{
+  CHECK_VALUE (result, NULL);
+
+  /* Verify that a sane error message was emitted.  */
+  CHECK_STRING_STARTS_WITH (gcc_jit_context_get_first_error (ctxt),
+			    "error invoking gcc driver");
+}
-- 
1.8.5.3