[LLD] [COFF] Always demangle the __imp_ prefix to __declspec(dllimport)

[mstorsjo]

Summary

This was requested by @ruiu in the review of D67301.

[mstorsjo]

@ruiu - does this look like what you want? For i386, do you want to keep the leading underscore, e.g. making __imp__foo into __declspec(dllimport) _foo, or have the demangling remove the underscore from _foo as well? This version removes that underscore, but it also changes the output for plain prefixless _foo symbols into foo.

[ruiu]

I think I prefer not to remove the leading underscore for i386 because as you wrote it makes the output ambiguous.

[mstorsjo]

Updated to never remove the extra leading underscore on i386 (except when demangling itanium C++ symbols).

[ruiu]

LGTM but I'd like to know what rnk thinks about this change.

[rnk]

lgtm

lld/test/COFF/undefined-symbol-itanium-i386.s

27 ↗

(On Diff #223166)

Fair enough. It's consistent with how we print the other x86 symbols above. (_main, _f1, etc)

lld/trunk/COFF/Symbols.cpp

 
 static_assert(sizeof(SymbolUnion) <= 48,
               "symbols should be optimized for memory usage");
 
 // Returns a symbol name for an error message.
 static std::string maybeDemangleSymbol(StringRef symName) {
   if (config->demangle) {
     std::string prefix;
-    StringRef demangleInput = symName;
-    if (demangleInput.consume_front("__imp_"))
+    StringRef prefixless = symName;
+    if (prefixless.consume_front("__imp_"))
       prefix = "__declspec(dllimport) ";
+    StringRef demangleInput = prefixless;
     if (config->machine == I386)
       demangleInput.consume_front("_");
     std::string demangled = demangle(demangleInput);
     if (demangled != demangleInput)
-      return prefix + demangled;
+      return prefix + demangle(demangleInput);
+    return (prefix + prefixless).str();
   }
   return symName;
 }
 std::string toString(coff::Symbol &b) {
   return maybeDemangleSymbol(b.getName());
 }
 std::string toCOFFString(const Archive::Symbol &b) {
   return maybeDemangleSymbol(b.getName());

lld/trunk/test/COFF/delayimports-error.test

 # RUN: mkdir -p %t.dir
 # RUN: yaml2obj < %p/Inputs/delayimports-error.yaml > %t1.obj
 # RUN: lld-link /out:%t.dir/foo.dll /dll %t1.obj /export:datasym,DATA /noentry
 
 # RUN: yaml2obj < %s > %t2.obj
 # RUN: not lld-link /out:%t.exe /entry:main %t2.obj %t.dir/foo.lib /delayload:foo.dll \
 # RUN:   /alternatename:__delayLoadHelper2=main /opt:noref >& %t.log
 # RUN: FileCheck %s < %t.log
 
-# CHECK: cannot delay-load foo.dll due to import of data: __imp_datasym
+# CHECK: cannot delay-load foo.dll due to import of data: __declspec(dllimport) datasym
 
 --- !COFF
 header:
   Machine:         IMAGE_FILE_MACHINE_AMD64
   Characteristics: []
 sections:
   - Name:            .text
     Characteristics: [ IMAGE_SCN_CNT_CODE, IMAGE_SCN_MEM_EXECUTE, IMAGE_SCN_MEM_READ ]

lld/trunk/test/COFF/duplicate.test

 # REQUIRES: x86
 RUN: llc -mtriple x86_64-windows-msvc -filetype obj -o alpha.obj %S/Inputs/alpha.ll
 RUN: llc -mtriple x86_64-windows-msvc -filetype obj -o beta.obj %S/Inputs/beta.ll
 RUN: lld-link /out:alpha.dll /dll alpha.obj /implib:alpha.lib
 RUN: not lld-link /out:beta.dll /dll alpha.obj beta.obj alpha.lib 2>&1 | FileCheck %s -check-prefix CHECK-ALPHA
 
 CHECK-ALPHA: error: duplicate symbol: f in {{.*}}alpha.obj and in alpha.dll
 
 RUN: llc -mtriple x86_64-windows-msvc -filetype obj -o gamma.obj %S/Inputs/gamma.ll
 RUN: not lld-link /out:gamma.exe /subsystem:console /entry:mainCRTStartup gamma.obj alpha.lib 2>&1 | FileCheck %s -check-prefix CHECK-GAMMA
 
-CHECK-GAMMA: error: duplicate symbol: __imp_f in {{.*}}gamma.obj and in alpha.dll
+CHECK-GAMMA: error: duplicate symbol: __declspec(dllimport) f in {{.*}}gamma.obj and in alpha.dll
 

lld/trunk/test/COFF/undefined-symbol-itanium-i386.s

 # REQUIRES: x86
 # RUN: llvm-mc -triple=i386-windows-gnu -filetype=obj -o %t.o %s
 # RUN: not lld-link /lldmingw /out:%t.exe %t.o 2>&1 | FileCheck %s
 # RUN: not lld-link /lldmingw /out:%t.exe /demangle %t.o 2>&1 | FileCheck %s
 # RUN: not lld-link /lldmingw /out:%t.exe /demangle:no %t.o 2>&1 | FileCheck --check-prefix=NODEMANGLE %s
 
 # NODEMANGLE: error: undefined symbol: __Z3fooi
 # NODEMANGLE: error: undefined symbol: __Z3barPKc
 # NODEMANGLE: error: undefined symbol: __imp___Z3bazv
 # NODEMANGLE: error: undefined symbol: _Z3fooi
+# NODEMANGLE: error: undefined symbol: __imp__cfunc
 
 # CHECK: error: undefined symbol: foo(int)
 # CHECK-NEXT: >>> referenced by {{.*}}.o:(_main)
 # CHECK-NEXT: >>> referenced by {{.*}}.o:(_main)
 # CHECK-EMPTY:
 # CHECK-NEXT: error: undefined symbol: bar(char const*)
 # CHECK-NEXT: >>> referenced by {{.*}}.o:(_main)
 # CHECK-NEXT: >>> referenced by {{.*}}.o:(_f1)
 # CHECK-EMPTY:
 # CHECK-NEXT: error: undefined symbol: __declspec(dllimport) baz()
 # CHECK-NEXT: >>> referenced by {{.*}}.o:(_f2)
 # CHECK-EMPTY:
 # CHECK-NEXT: error: undefined symbol: _Z3fooi
 # CHECK-NEXT: >>> referenced by {{.*}}.o:(_f2)
+# CHECK-EMPTY:
+# CHECK-NEXT: error: undefined symbol: __declspec(dllimport) _cfunc
+# CHECK-NEXT: >>> referenced by {{.*}}.o:(_f2)
 
         .section        .text,"xr",one_only,_main
 .globl _main
 _main:
   call  __Z3fooi
   call  __Z3fooi
   call  __Z3barPKc
 
 _f1:
   call  __Z3barPKc
 .Lfunc_end1:
 
         .section        .text,"xr",one_only,_f2
 .globl _f2
 _f2:
   call  *__imp___Z3bazv
   call  _Z3fooi
+  call  *__imp__cfunc

lld/trunk/test/COFF/undefined-symbol.s

 # CHECK-EMPTY:
 # CHECK-NEXT: error: undefined symbol: int __cdecl bar(void)
 # CHECK-NEXT: >>> referenced by {{.*}}.obj:(main)
 # CHECK-NEXT: >>> referenced by {{.*}}.obj:(f1)
 # CHECK-EMPTY:
 # CHECK-NEXT: error: undefined symbol: __declspec(dllimport) int __cdecl baz(void)
 # CHECK-NEXT: >>> referenced by {{.*}}.obj:(f2)
 # CHECK-EMPTY:
-# CHECK-NEXT: error: undefined symbol: __imp_undecorated
+# CHECK-NEXT: error: undefined symbol: __declspec(dllimport) undecorated
 # CHECK-NEXT: >>> referenced by {{.*}}.obj:(f2)
 
         .section        .text,"xr",one_only,main
 .globl main
 main:
   call  "?foo@@YAHXZ"
   call  "?foo@@YAHXZ"
   call  "?bar@@YAHXZ"