[PATCH, cpp] Fix line directive bug‏

[Nicholas Ormrod <nicholas dot ormrod at hotmail dot com>]

PR preprocessor/60723

Description:

When line directives are inserted into the expansion of a macro, the line
directive may erroneously specify the file as being a system file. This
causes certain warnings to be suppressed in the rest of the file.

The fact that line directives are ever inserted into a macro is itself a
half-bug. Please see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60723 for
full details.


Patch:

Information for locations is, for similar pieces of data, read from a
LOCATION_* macro. The sysp read which was causing the error was using an
inconsistent method to read the data. Resolving this is a two-line fix.


Testing:

make check-gcc on a clean build generates 104754 expected passes, 13
unexpected failures, 245 expected failures, and 1624 unsupported tests. The
new test case, on the clean checkout, generates one expected pass and one
unexpected failure. Once the changes are in, the original test numbers are
unchanged, but the new test case generates two expected passes.


Details:

2014-06-10  Nicholas Ormrod  <nicholas.ormrod@hotmail.com>

    PR preprocessor/60723
    * input.h: Add LOCATION_* macro for sysp
    * c-family/c-ppoutput.c (print_line_1): Use LOCATION_SYSP for
    consistency with other LOCATION_* accesses.
    * testsuite/gcc.dg/cpp/syshdr4.c: New test case.
    * testsuite/gcc.dg/cpp/syshdr4.h: New test case.


diff --git a/gcc/c-family/c-ppoutput.c b/gcc/c-family/c-ppoutput.c
index f3b5fa4..21484d9 100644
--- a/gcc/c-family/c-ppoutput.c
+++ b/gcc/c-family/c-ppoutput.c
@@ -384,7 +384,7 @@ print_line_1 (source_location src_loc, const char
*special_flags, FILE *stream)
            print.src_line == 0 ? 1 : print.src_line,
            to_file_quoted, special_flags);

-      sysp = in_system_header_at (src_loc);
+      sysp = LOCATION_SYSP(src_loc);
       if (sysp == 2)
     fputs (" 3 4", stream);
       else if (sysp == 1)
diff --git a/gcc/input.h b/gcc/input.h
index d910bb8..ff42e04 100644
--- a/gcc/input.h
+++ b/gcc/input.h
@@ -51,6 +51,7 @@ extern location_t input_location;
#define LOCATION_FILE(LOC) ((expand_location (LOC)).file)
#define LOCATION_LINE(LOC) ((expand_location (LOC)).line)
#define LOCATION_COLUMN(LOC)((expand_location (LOC)).column)
+#define LOCATION_SYSP(LOC) ((expand_location (LOC)).sysp)
#define LOCATION_LOCUS(LOC) \
   ((IS_ADHOC_LOC (LOC)) ? get_location_from_adhoc_loc (line_table, LOC) \
    : (LOC))
diff --git a/gcc/testsuite/gcc.dg/cpp/syshdr4.c
b/gcc/testsuite/gcc.dg/cpp/syshdr4.c
new file mode 100644
index 0000000..8296bed
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/cpp/syshdr4.c
@@ -0,0 +1,23 @@
+/* Contributed by Nicholas Ormrod */
+/* Origin: PR preprocessor/60723 */
+
+/* This tests that multi-line macro callsites, which are defined
+   in system headers and whose expansion contains a builtin followed
+   by a non-builtin token, do not generate a line directive that
+   mark the current file as being a system file, when performing
+   non-integrated preprocessing. */
+/* System files suppress div-by-zero warnings, so the presence of
+   such indicates the lack of the bug. */
+
+/* { dg-do compile } */
+/* { dg-options -no-integrated-cpp } */
+
+#include "syshdr4.h"
+FOO(
+)
+
+int
+foo()
+{
+  return 1 / 0; /* { dg-warning "div-by-zero" } */
+}
diff --git a/gcc/testsuite/gcc.dg/cpp/syshdr4.h
b/gcc/testsuite/gcc.dg/cpp/syshdr4.h
new file mode 100644
index 0000000..e699299
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/cpp/syshdr4.h
@@ -0,0 +1,3 @@
+#pragma GCC system_header
+
+#define FOO() int line = __LINE__ ;


I have been working on a virtual Ubuntu 12.04 box.

gcc -v:
Using built-in specs.
COLLECT_GCC=./bin/gcc
COLLECT_LTO_WRAPPER=/home/njormrod/src/gcc/new_build/bin/../libexec/gcc/i686
-pc-linux-gnu/4.10.0/lto-wrapper
Target: i686-pc-linux-gnu
Configured with: ../gcc/configure --prefix=/home/njormrod/src/gcc/_build
--disable-multilib --enable-languages=c,c++ --disable-libgcj
Thread model: posix
gcc version 4.10.0 20140610 (experimental) (GCC)



Cheers,
Nicholas Ormrod