[ELF] Error if -r --gdb-index are used together

[ruiu]

Instead of doing this, maybe we should report an error when -gdb-index is used with -r. I don't think there's a valid use case of giving the two flags at the same time.

[MaskRay]

.

[ruiu]

LGTM

[dblaikie]

Would be good to have an explanation about why these options are incompatible in the commit message (missed that opportunity) and maybe in the source.

Is the schema in gdb_index unable to handle multiple code sections, for example?

[dblaikie]

This might not be especially useful - the gnu_pubnames sections don't
describe which CU they are for (if I recall correctly), so once you've got
multiple CUs in a single object file (admittedly, this happens in LTO too,
adn I'm not sure how that's handled) it might not be terribly useful. I'm
not sure what lld's gdb-index does when consuming an object with multiple
CUs in it, for example.

ELF/Driver.cpp

static void checkOptions(opt::InputArgList &Args) {
   if (!Config->Relocatable && !Config->DefineCommon)
     error("-no-define-common not supported in non relocatable output");
 
   if (Config->Relocatable) {
     if (Config->Shared)
       error("-r and -shared may not be used together");
     if (Config->GcSections)
       error("-r and --gc-sections may not be used together");
+    if (Config->GdbIndex)
+      error("-r and --gdb-index may not be used together");
     if (Config->ICF)
       error("-r and --icf may not be used together");
     if (Config->Pie)
       error("-r and -pie may not be used together");
   }
 }
 
 static const char *getReproduceOption(opt::InputArgList &Args) {

test/ELF/driver.test

 ## Attempt to use -r and -shared together
 # RUN: not ld.lld -r -shared %t -o %tfail 2>&1 | FileCheck -check-prefix=ERR2 %s
 # ERR2: -r and -shared may not be used together
 
 ## Attempt to use -r and --gc-sections together
 # RUN: not ld.lld -r --gc-sections %t -o %tfail 2>&1 | FileCheck -check-prefix=ERR3 %s
 # ERR3: -r and --gc-sections may not be used together
 
+## Attempt to use -r and --gdb-index together
+# RUN: not ld.lld -r --gdb-index %t -o %tfail 2>&1 | FileCheck -check-prefix=ERR4 %s
+# ERR4: -r and --gdb-index may not be used together
+
 ## Attempt to use -r and --icf together
-# RUN: not ld.lld -r --icf=all %t -o %tfail 2>&1 | FileCheck -check-prefix=ERR4 %s
-# ERR4: -r and --icf may not be used together
+# RUN: not ld.lld -r --icf=all %t -o %tfail 2>&1 | FileCheck -check-prefix=ERR5 %s
+# ERR5: -r and --icf may not be used together
 
 ## Attempt to use -r and -pie together
-# RUN: not ld.lld -r -pie %t -o %tfail 2>&1 | FileCheck -check-prefix=ERR5 %s
-# ERR5: -r and -pie may not be used together
+# RUN: not ld.lld -r -pie %t -o %tfail 2>&1 | FileCheck -check-prefix=ERR6 %s
+# ERR6: -r and -pie may not be used together
 
 ## Attempt to use -shared and -pie together
-# RUN: not ld.lld -shared -pie %t -o %tfail 2>&1 | FileCheck -check-prefix=ERR6 %s
-# ERR6: -shared and -pie may not be used together
+# RUN: not ld.lld -shared -pie %t -o %tfail 2>&1 | FileCheck -check-prefix=ERR7 %s
+# ERR7: -shared and -pie may not be used together
 
 ## "--output=foo" is equivalent to "-o foo".
-# RUN: not ld.lld %t --output=/no/such/file 2>&1 | FileCheck -check-prefix=ERR7 %s
-# ERR7: cannot open output file /no/such/file
+# RUN: not ld.lld %t --output=/no/such/file 2>&1 | FileCheck -check-prefix=ERR8 %s
+# ERR8: cannot open output file /no/such/file
 
 ## "-output=foo" is equivalent to "-o utput=foo".
-# RUN: not ld.lld %t -output=/no/such/file 2>&1 | FileCheck -check-prefix=ERR8 %s
-# ERR8: cannot open output file utput=/no/such/file
+# 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=ERR9 %s
-# ERR9: unknown -z value: foo
+# RUN: not ld.lld %t -z foo 2>&1 | FileCheck -check-prefix=ERR10 %s
+# ERR10: unknown -z value: foo
 
-# RUN: not ld.lld %t -z max-page-size 2>&1 | FileCheck -check-prefix=ERR10 %s
-# ERR10: unknown -z value: max-page-size
+# RUN: not ld.lld %t -z max-page-size 2>&1 | FileCheck -check-prefix=ERR11 %s
+# ERR11: unknown -z value: max-page-size
 
 .globl _start
 _start:
   nop