[LLD] [COFF] Print a warning when using /dependentloadflag without load config

Author: mati865

lld/COFF/Driver.cpp

@@ -2307,8 +2307,11 @@ void LinkerDriver::linkerMain(ArrayRef<const char *> argsArr) {
 
   // Handle /dependentloadflag
   for (auto *arg :
-       args.filtered(OPT_dependentloadflag, OPT_dependentloadflag_opt))
+       args.filtered(OPT_dependentloadflag, OPT_dependentloadflag_opt)) {
     parseDependentLoadFlags(arg);
+    if (!ctx.symtab.findUnderscore("_load_config_used"))
+      warn("_load_config_used not found, /delayloadflag will have no effect");
+  }
 
   if (tar) {
     llvm::TimeTraceScope timeScope("Reproducer: response file");

lld/test/COFF/dependentflags.test

@@ -20,6 +20,9 @@ RUN: not lld-link %S/Inputs/precomp-a.obj %t.ldcfg.obj /out:%t.exe /nodefaultlib
 RUN: not lld-link %S/Inputs/precomp-a.obj %t.ldcfg.obj /out:%t.exe /nodefaultlib /force /dependentloadflag:zz 2>&1 | FileCheck %s --check-prefix FAIL
 RUN: not lld-link %S/Inputs/precomp-a.obj %t.ldcfg.obj /out:%t.exe /nodefaultlib /force /dependentloadflag:0xf0000 2>&1 | FileCheck %s --check-prefix FAIL-RANGE
 
+// ---- Warn if _load_config_used is missing
+RUN: lld-link %S/Inputs/precomp-a.obj /out:%t.exe /nodefaultlib /force /dependentloadflag:0x800 2>&1 | FileCheck %s --check-prefix WARN-NOBASE
+RUN: lld-link %S/Inputs/precomp-a.obj %t.ldcfg.obj /out:%t.exe /nodefaultlib /force /dependentloadflag:0x800 2>&1 | FileCheck %s --allow-empty --check-prefix NO-WARN
 
 BASE: DependentLoadFlags: 0x0
 FLAGS-800: DependentLoadFlags: 0x800
@@ -29,3 +32,5 @@ FAIL: lld-link: error: /dependentloadflag: invalid argument: zz
 FAIL-RANGE: lld-link: error: /dependentloadflag: invalid argument: 0xf0000
 FAIL-NOARG: lld-link: error: /dependentloadflag: no argument specified
 
+WARN-NOBASE: lld-link: warning: _load_config_used not found, /delayloadflag will have no effect
+NO-WARN-NOT: lld-link: warning: _load_config_used not found, /delayloadflag will have no effect