Re: [PATCH] preprocessor/58580 - preprocessor goes OOM with warning for zero literals

[Dodji Seketeli <dodji@redhat.com>]

Jakub Jelinek <jakub@redhat.com> writes:

> On Fri, Jan 24, 2014 at 04:40:52PM +0100, Dodji Seketeli wrote:
>> > The patch causes http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59935 .
>> > The follow-up patch (fp == NULL check) doesn't help.
>> 
>> I am looking into that, sorry for the inconvenience.
>
> I'd say we want something like following.  Note that while the c == NULL
> bailout would be usually sufficient, if you'll do:
> echo foobar > '<command-line>'
> it would still crash.  Line 0 is used only for the special locations
> (command line, built-in macros) and there is no file associated with it
> anyway.
>
> --- gcc/input.c.jj	2014-01-24 16:32:34.000000000 +0100
> +++ gcc/input.c	2014-01-24 16:41:42.012671452 +0100
> @@ -698,7 +698,13 @@ location_get_source_line (expanded_locat
>    static char *buffer;
>    static ssize_t len;
>  
> -  fcache * c = lookup_or_add_file_to_cache_tab (xloc.file);
> +  if (xloc.line == 0)
> +    return NULL;
> +
> +  fcache *c = lookup_or_add_file_to_cache_tab (xloc.file);
> +  if (c == NULL)
> +    return NULL;
> +
>    bool read = read_line_num (c, xloc.line, &buffer, &len);
>  
>    if (read && line_len)

Indeed.

Though, I am testing the patch below that makes read_line_num gracefully
handle empty caches or zero locations.  The rest of the code should just
work with that as is.

	* input.c (read_line_num): Gracefully handle non-file locations or
	empty caches.

diff --git a/gcc/input.c b/gcc/input.c
index 547c177..b05e1da 100644
--- a/gcc/input.c
+++ b/gcc/input.c
@@ -600,7 +600,8 @@ static bool
 read_line_num (fcache *c, size_t line_num,
 	       char ** line, ssize_t *line_len)
 {
-  gcc_assert (line_num > 0);
+  if (!c || line_num < 1)
+    return false;
 
   if (line_num <= c->line_num)
     {
diff --git a/gcc/testsuite/c-c++-common/cpp/warning-zero-location.c b/gcc/testsuite/c-c++-common/cpp/warning-zero-location.c
new file mode 100644
index 0000000..04a06b2
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/cpp/warning-zero-location.c
@@ -0,0 +1,6 @@
+/*
+   { dg-options "-D _GNU_SOURCE" }
+   { dg-do compile }
+ */
+
+#define _GNU_SOURCE 	/* { dg-warning "redefined" } */
-- 
		Dodji