Segfault adding a label to a function

[dvarrazzo]

Trying to run the checker on psycopg again :tada: Trying with psycopg/psycopg2@23438ce780396b1ffe87ae05953af0976b249e0b and gcc-python-plugin master at 41f52bd3ff54847af5ecd878887ecb18e7bfed93. Tested on Ubuntu 18.04 with gcc 5.5.0 and 6.5.0 (packages gcc-5 and gcc-6).

just a CC=gcc-with-cpychecker make fails on a file too complex, so I'm trying to run a normal make and using the generated commands to test the source files one-by-one. In particular here I'm playing with the file psycopg/utils.c so in order to get a command line you can use:

$ make | grep utils.c
x86_64-linux-gnu-gcc [options] -c psycopg/utils.c [more options]

and run instead:

$ CC_FOR_CPYCHECKER=gcc-6 /path/to/gcc-with-cpychecker [options] -c psycopg/utils.c [more options]

(Note that the -DPSYCOPG_VERSION option contain spaces so it needs quoting).

Testing the file psycopg/utils.c, a warning on the function psycopg_escape_string() being too complex is generated (is it?). Trying munging, applying the seemingly harmless patch:

piro@makkuro:~/dev/psycopg2$ git diff
diff --git a/psycopg/utils.c b/psycopg/utils.c
index 261810f..c135072 100644
--- a/psycopg/utils.c
+++ b/psycopg/utils.c
@@ -89,6 +89,7 @@ psycopg_escape_string(connectionObject *conn, const char *from, Py_ssize_t len,
     if (tolen)
         *tolen = ql+eq+2;

+exit:
     return to;
 }

results in a segfault with the following output:

psycopg/utils.c: In function ‘psycopg_escape_string’:
psycopg/utils.c:92:1: warning: label ‘exit’ defined but not used [-Wunused-label]
 exit:
 ^~~~
*** WARNING *** there are active plugins, do not report this as a bug unless you can reproduce it without enabling any plugins.
Event                            | Plugins
PLUGIN_FINISH_DECL               | python
PLUGIN_FINISH                    | python
PLUGIN_ATTRIBUTES                | python
psycopg/utils.c:90:16: internal compiler error: Segmentation fault
         *tolen = ql+eq+2;
         ~~~~~~~^~~~~~~~~
0x7f68dbae4f1a impl_execute
    /home/piro/dev/fs/gcc-python-plugin/gcc-python-pass.c:134
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <file:///usr/share/doc/gcc-6/README.Bugs> for instructions.

Same problem with gcc-5. gcc-7 doesn't deal with refcount check so not playing with it.