[PATCH] D114748: [ELF] Change -z unknown from error to warning

[Fangrui Song via Phabricator via llvm-commits]

MaskRay created this revision.
MaskRay added reviewers: jrtc27, peter.smith.
Herald added subscribers: arichardson, emaste.
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There is a trend of having more optional options (usually security
hardening related) like -z cet-report=, -z bti-report=, -z force-bti.
If ld.lld 14.0.0 uses a warning, in 15/16/17/... timeframe when people
add new options to software, they can worry less about linker errors on ld.lld 14.0.0.

In some cases `-z foo` does essential work where a silent ignore can be
problematic, but the user has received a warning. From my observation, the
doing-essential-work `-z foo` is much fewer than the converse. In addition,
the user who cares can use `--fatal-warnings`. It is unclear whether we need
something like `clang -Wunknown-warning-option`

If we ever run into unfortunate transition like `-z start-stop-gc`, the
affected software can blindly add the `-z` option, without worrying it
may cause a linker error to LLD 14.0.0.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D114748

Files:
  lld/ELF/Driver.cpp
  lld/test/ELF/driver.test


Index: lld/test/ELF/driver.test
===================================================================
--- lld/test/ELF/driver.test
+++ lld/test/ELF/driver.test
@@ -58,12 +58,12 @@
 # RUN: not ld.lld %t -output=/no/such/file 2>&1 | FileCheck -check-prefix=ERR9 %s
 # ERR9: cannot open output file utput=/no/such/file
 
-# RUN: not ld.lld %t -z foo 2>&1 | FileCheck -check-prefix=ERR10 %s
-# RUN: not ld.lld %t -z foo --version 2>&1 | FileCheck -check-prefix=ERR10 %s
-# ERR10: unknown -z value: foo
+# RUN: ld.lld %t -z foo 2>&1 | FileCheck -check-prefix=ERR10 %s
+# RUN: ld.lld %t -z foo --version 2>&1 | FileCheck -check-prefix=ERR10 %s
+# ERR10: warning: unknown -z value: foo
 
 ## Check we report "unknown -z value" error even with -v.
-# RUN: not ld.lld %t -z foo -v 2>&1 | FileCheck -check-prefix=ERR10 %s
+# RUN: ld.lld %t -z foo -v 2>&1 | FileCheck -check-prefix=ERR10 %s
 
 # RUN: not ld.lld %t -z max-page-size 2>&1 | FileCheck -check-prefix=ERR11 %s
 # ERR11: unknown -z value: max-page-size
Index: lld/ELF/Driver.cpp
===================================================================
--- lld/ELF/Driver.cpp
+++ lld/ELF/Driver.cpp
@@ -464,7 +464,7 @@
 static void checkZOptions(opt::InputArgList &args) {
   for (auto *arg : args.filtered(OPT_z))
     if (!isKnownZFlag(arg->getValue()))
-      error("unknown -z value: " + StringRef(arg->getValue()));
+      warn("unknown -z value: " + StringRef(arg->getValue()));
 }
 
 void LinkerDriver::linkerMain(ArrayRef<const char *> argsArr) {


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