[gcc r12-6876] analyzer: fix missing uninit warning on args to stdio builtins [PR104224]

[David Malcolm <dmalcolm@gcc.gnu.org>]

https://gcc.gnu.org/g:9ff3e2368d86c1bf7d1e8876a14e58c0d6617ffe

commit r12-6876-g9ff3e2368d86c1bf7d1e8876a14e58c0d6617ffe
Author: David Malcolm <dmalcolm@redhat.com>
Date:   Tue Jan 25 14:10:46 2022 -0500

    analyzer: fix missing uninit warning on args to stdio builtins [PR104224]
    
    We were failing to check for uninitialized arguments to stdio builtins,
    such as when passing local "go" to the call to "printf" in "main" in
    the testcase.
    
    gcc/analyzer/ChangeLog:
            PR analyzer/104224
            * region-model.cc (region_model::check_call_args): New.
            (region_model::on_call_pre): Call it when ignoring stdio builtins.
            * region-model.h (region_model::check_call_args): New decl
    
    gcc/testsuite/ChangeLog:
            PR analyzer/104224
            * gcc.dg/analyzer/pr104224.c: New test.
    
    Signed-off-by: David Malcolm <dmalcolm@redhat.com>

Diff:
---
 gcc/analyzer/region-model.cc             |  11 ++++
 gcc/analyzer/region-model.h              |   2 +
 gcc/testsuite/gcc.dg/analyzer/pr104224.c | 106 +++++++++++++++++++++++++++++++
 3 files changed, 119 insertions(+)

diff --git a/gcc/analyzer/region-model.cc b/gcc/analyzer/region-model.cc
index f6b7f986a39..a559bc84eb0 100644
--- a/gcc/analyzer/region-model.cc
+++ b/gcc/analyzer/region-model.cc
@@ -1044,6 +1044,16 @@ region_model::on_stmt_pre (const gimple *stmt,
     }
 }
 
+/* Ensure that all arguments at the call described by CD are checked
+   for poisoned values, by calling get_rvalue on each argument.  */
+
+void
+region_model::check_call_args (const call_details &cd) const
+{
+  for (unsigned arg_idx = 0; arg_idx < cd.num_args (); arg_idx++)
+    cd.get_arg_svalue (arg_idx);
+}
+
 /* Update this model for the CALL stmt, using CTXT to report any
    diagnostics - the first half.
 
@@ -1173,6 +1183,7 @@ region_model::on_call_pre (const gcall *call, region_model_context *ctxt,
 	    /* These stdio builtins have external effects that are out
 	       of scope for the analyzer: we only want to model the effects
 	       on the return value.  */
+	    check_call_args (cd);
 	    break;
 	  }
       else if (is_named_call_p (callee_fndecl, "malloc", call, 1))
diff --git a/gcc/analyzer/region-model.h b/gcc/analyzer/region-model.h
index c78efe8f215..40958842bce 100644
--- a/gcc/analyzer/region-model.h
+++ b/gcc/analyzer/region-model.h
@@ -832,6 +832,8 @@ class region_model
   void check_region_for_read (const region *src_reg,
 			      region_model_context *ctxt) const;
 
+  void check_call_args (const call_details &cd) const;
+
   /* Storing this here to avoid passing it around everywhere.  */
   region_model_manager *const m_mgr;
 
diff --git a/gcc/testsuite/gcc.dg/analyzer/pr104224.c b/gcc/testsuite/gcc.dg/analyzer/pr104224.c
new file mode 100644
index 00000000000..8f69d72befa
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/analyzer/pr104224.c
@@ -0,0 +1,106 @@
+#include <stdio.h>
+
+struct test {
+        int one;
+        int two;
+};
+
+void func2(const struct test *t)
+{
+        if (t->one == 0)
+                printf("init func2\n");
+
+        if (t->two == 0)  /* { dg-warning "uninitialized" } */
+                printf("uninit func2\n");
+}
+
+void func1(struct test *t)
+{
+        t->one = 1;
+        func2(t);
+}
+
+int func3(int num)
+{
+        if (num)
+                return num;
+        else
+                return 0;
+}
+
+void func4(int *a, int max)
+{
+        int i;
+        // skip the first
+        for (i=1; i<max; i++)
+                a[i] = 0;
+}
+
+void func5(const int *a, int max)
+{
+        /* a[0] is uninitialized, but the rest of the array is initialized.  */
+        int i;
+        for (i=0; i<max; i++) {
+                if (a[i]) /* { dg-warning "uninitialized" "" { xfail *-*-* } } */
+                        printf("func5: %d\n", i);
+        }
+}
+
+int func6(const int *num)
+{
+        if (*num)  /* { dg-warning "uninitialized" } */
+                return *num;  /* { dg-warning "uninitialized" } */
+        else
+                return 0;
+}
+
+int j;
+int func7(void)
+{
+        return j;  /* { dg-bogus "uninitialized" } */
+}
+
+void func8(const int *a, int max)
+{
+        int i;
+        for (i=0; i<max; i++) {
+                if (a[i]) /* { dg-warning "uninitialized" } */
+                        printf("func8: %d\n", i);
+        }
+}
+
+enum {RED, AMBER, GREEN, BLACK};
+
+int main(void)
+{
+        struct test t;
+        int num;
+        int arry[10];
+        int arry_2[10];
+        int go;
+        int color = BLACK;
+
+        func1(&t);
+        func3(num);  /* { dg-warning "use of uninitialized value 'num'" } */
+        func4(arry, 10);
+        func5(arry, 10);
+        func6(&num);
+
+        printf("num: %d\n", num);  /* { dg-warning "use of uninitialized value 'num'" } */
+        printf("func7: %d\n", func7());
+        func8(arry_2, 10);
+
+        switch (color) {
+        case RED:
+        case AMBER:
+                go = 0;
+                break;
+        case GREEN:
+                go = 1;
+                break;
+        }
+
+        printf("go :%d\n", go); /* { dg-warning "use of uninitialized value 'go'" } */
+
+        return 0;
+}