[PATCH] ipa/102762 - fix ICE with invalid __builtin_va_arg_pack () use

[Richard Biener via Gcc-patches]

We have to be careful to not break the argument space calculation.
If there's not enough arguments just do not append any.

Bootstrapped and tested on x86_64-unknown-linux-gnu, pushed.

2021-10-15  Richard Biener  <rguent...@suse.de>

        PR ipa/102762
        * tree-inline.c (copy_bb): Avoid underflowing nargs.

        * gcc.dg/torture/pr102762.c: New testcase.
---
 gcc/testsuite/gcc.dg/torture/pr102762.c | 11 +++++++++++
 gcc/tree-inline.c                       |  8 +++++++-
 2 files changed, 18 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/gcc.dg/torture/pr102762.c

diff --git a/gcc/testsuite/gcc.dg/torture/pr102762.c 
b/gcc/testsuite/gcc.dg/torture/pr102762.c
new file mode 100644
index 00000000000..67c6b00ccea
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr102762.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* We fail to diagnose the invalid __builtin_va_arg_pack use with -flto.  */
+/* { dg-skip-if "" { *-*-* } { "-flto" } { "" } } */
+
+void log_bad_request();
+void foo(a, b)
+     int a, b;
+{
+  log_bad_request(0, __builtin_va_arg_pack());  /* { dg-error "invalid use" } 
*/
+  foo(0);
+}
diff --git a/gcc/tree-inline.c b/gcc/tree-inline.c
index e292a144967..b2c58ac4c3b 100644
--- a/gcc/tree-inline.c
+++ b/gcc/tree-inline.c
@@ -2117,7 +2117,13 @@ copy_bb (copy_body_data *id, basic_block bb,
              size_t nargs = nargs_caller;
 
              for (p = DECL_ARGUMENTS (id->src_fn); p; p = DECL_CHAIN (p))
-               nargs--;
+               {
+                 /* Avoid crashing on invalid IL that doesn't have a
+                    varargs function or that passes not enough arguments.  */
+                 if (nargs == 0)
+                   break;
+                 nargs--;
+               }
 
              /* Create the new array of arguments.  */
              size_t nargs_callee = gimple_call_num_args (call_stmt);
-- 
2.31.1