[committed] analyzer: fix ICE on assignment from STRING_CST when building path [PR100011]

[David Malcolm via Gcc-patches]

Successfully bootstrapped & regrtested on x86_64-pc-linux-gnu.
Pushed to trunk as r11-8117-gec633d3777bd71f7bde5e671b61ec18e5b7b43ea.

gcc/analyzer/ChangeLog:
        PR analyzer/100011
        * region-model.cc (region_model::on_assignment): Avoid NULL
        dereference if ctxt is NULL when assigning from a STRING_CST.

gcc/testsuite/ChangeLog:
        PR analyzer/100011
        * gcc.dg/analyzer/pr100011.c: New test.
---
 gcc/analyzer/region-model.cc             |  2 +-
 gcc/testsuite/gcc.dg/analyzer/pr100011.c | 16 ++++++++++++++++
 2 files changed, 17 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/gcc.dg/analyzer/pr100011.c

diff --git a/gcc/analyzer/region-model.cc b/gcc/analyzer/region-model.cc
index 2d3880bf8cc..c7038dd2d4b 100644
--- a/gcc/analyzer/region-model.cc
+++ b/gcc/analyzer/region-model.cc
@@ -726,7 +726,7 @@ region_model::on_assignment (const gassign *assign, 
region_model_context *ctxt)
           access will "inherit" the individual chars.  */
        const svalue *rhs_sval = get_rvalue (rhs1, ctxt);
        m_store.set_value (m_mgr->get_store_manager(), lhs_reg, rhs_sval,
-                          BK_default, ctxt->get_uncertainty ());
+                          BK_default, ctxt ? ctxt->get_uncertainty () : NULL);
       }
       break;
     }
diff --git a/gcc/testsuite/gcc.dg/analyzer/pr100011.c 
b/gcc/testsuite/gcc.dg/analyzer/pr100011.c
new file mode 100644
index 00000000000..228cfdfeac7
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/analyzer/pr100011.c
@@ -0,0 +1,16 @@
+/* { dg-require-effective-target signal } */
+
+#include <stdlib.h>
+#include <signal.h>
+
+void terminate(int sig)
+{
+  char buf[64] = { 0 };
+  exit(1); /* { dg-warning "call to 'exit' from within signal handler" } */
+}
+
+int main(int argc, char **argv)
+{
+  signal(0, terminate); /* { dg-message "registering 'terminate' as signal 
handler" } */
+  return 0;
+}
-- 
2.26.2