[clang] [clang][bytecode] Error if calls have fewer arguments than parameters (PR #155151)

[Timm Baeder via cfe-commits]

https://github.com/tbaederr updated https://github.com/llvm/llvm-project/pull/155151

>From 6e9e9659ce2014d56780de5ed67697753ee6ad70 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Timm=20B=C3=A4der?= <tbaeder at redhat.com>
Date: Tue, 26 Aug 2025 05:53:58 +0200
Subject: [PATCH] Fixup

---
 clang/lib/AST/ByteCode/Compiler.cpp |  6 ++++++
 clang/test/AST/ByteCode/c.c         | 11 +++++++++++
 2 files changed, 17 insertions(+)

diff --git a/clang/lib/AST/ByteCode/Compiler.cpp b/clang/lib/AST/ByteCode/Compiler.cpp
index c36cb644282d8..c5af7b8450ed7 100644
--- a/clang/lib/AST/ByteCode/Compiler.cpp
+++ b/clang/lib/AST/ByteCode/Compiler.cpp
@@ -5228,6 +5228,12 @@ bool Compiler<Emitter>::VisitCallExpr(const CallExpr *E) {
     const Function *Func = getFunction(FuncDecl);
     if (!Func)
       return false;
+
+    // In error cases, the function may be called with fewer arguments than
+    // parameters.
+    if (E->getNumArgs() < Func->getNumWrittenParams())
+      return false;
+
     assert(HasRVO == Func->hasRVO());
 
     bool HasQualifier = false;
diff --git a/clang/test/AST/ByteCode/c.c b/clang/test/AST/ByteCode/c.c
index 73469d7fd6cc4..258891453a0dc 100644
--- a/clang/test/AST/ByteCode/c.c
+++ b/clang/test/AST/ByteCode/c.c
@@ -347,3 +347,14 @@ const int compared = strcmp(_str, (const char *)_str2); // all-error {{initializ
 
 const int compared2 = strcmp(strcmp, _str); // all-warning {{incompatible pointer types}} \
                                             // all-error {{initializer element is not a compile-time constant}}
+
+int foo(x) // all-warning {{a function definition without a prototype is deprecated in all versions of C}}
+int x;
+{
+  return x;
+}
+
+void bar() { // pedantic-warning {{a function declaration without a prototype}}
+  int x;
+  x = foo(); // all-warning {{too few arguments}}
+}