[ELF] --sysroot: change sysrooted script to not fall back for an absolute path

[MaskRay]

Summary

Modify the D13209 logic: for a script inside the sysroot, if an absolute path
does not exist, report an error instead of falling back to the path without the
sysroot prefix.

This matches GNU ld, which makes sense to me: we don't want to find an arbitrary
file in the host.

[ikudrin]

LGTM

lld/ELF/ScriptParser.cpp

void ScriptParser::readDefsym(StringRef name) {
   SymbolAssignment *cmd = make<SymbolAssignment>(name, e, getCurrentLocation());
   script->sectionCommands.push_back(cmd);
 }
 
 void ScriptParser::addFile(StringRef s) {
   if (isUnderSysroot && s.startswith("/")) {
     SmallString<128> pathData;
     StringRef path = (config->sysroot + s).toStringRef(pathData);
-    if (sys::fs::exists(path)) {
+    if (sys::fs::exists(path))
       driver->addFile(saver.save(path), /*withLOption=*/false);
-      return;
-    }
-  }
+    else
+      setError("cannot find " + s + " inside " + config->sysroot);
 
   if (s.startswith("/")) {
     // Case 1: s is an absolute path. Just open it.
     driver->addFile(s, /*withLOption=*/false);
   } else if (s.startswith("=")) {
     // Case 2: relative to the sysroot.
     if (config->sysroot.empty())
       driver->addFile(s.substr(1), /*withLOption=*/false);

lld/test/ELF/linkerscript/group.s

 # REQUIRES: x86
+# UNSUPPORTED: system-windows
 
 # RUN: mkdir -p %t.dir
 # RUN: rm -f %t.dir/libxyz.a
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux \
 # RUN:   %p/Inputs/libsearch-st.s -o %t2.o
 # RUN: llvm-ar rcs %t.dir/libxyz.a %t2.o
 

 
 # RUN: echo "GROUP(\"%t\" libxyz.a )" > %t.script
 # RUN: not ld.lld -o /dev/null %t.script  2>/dev/null
 # RUN: ld.lld -o %t2 %t.script -L%t.dir
 # RUN: llvm-readobj %t2 > /dev/null
 
 # RUN: echo "GROUP(\"%t\" /libxyz.a )" > %t.script
 # RUN: echo "GROUP(\"%t\" /libxyz.a )" > %t.dir/xyz.script
-# RUN: not ld.lld -o /dev/null %t.script 2>/dev/null
-# RUN: not ld.lld -o /dev/null %t.script --sysroot=%t.dir  2>/dev/null
-# RUN: ld.lld -o %t2 %t.dir/xyz.script --sysroot=%t.dir
-# RUN: llvm-readobj %t2 > /dev/null
+# RUN: not ld.lld -o /dev/null %t.script 2>&1 | FileCheck %s --check-prefix=CANNOT_OPEN -DFILE=/libxyz.a
+# RUN: not ld.lld -o /dev/null %t.script --sysroot=%t.dir 2>&1 | FileCheck %s --check-prefix=CANNOT_OPEN -DFILE=/libxyz.a
+
+## Since %t.dir/%t does not exist, report an error, instead of falling back to %t
+## without the syroot prefix.
+# RUN: not ld.lld -o /dev/null %t.dir/xyz.script --sysroot=%t.dir 2>&1 | FileCheck %s --check-prefix=CANNOT_FIND_SYSROOT -DTMP=%t
+
+# CANNOT_FIND_SYSROOT:      error: {{.*}}xyz.script:1: cannot find [[TMP]] inside [[TMP]].dir
+# CANNOT_FIND_SYSROOT-NEXT: >>> GROUP({{.*}}
 
 # RUN: echo "GROUP(\"%t.script2\")" > %t.script1
 # RUN: echo "GROUP(\"%t\")" > %t.script2
 # RUN: ld.lld -o %t2 %t.script1
 # RUN: llvm-readobj %t2 > /dev/null
 
 # RUN: echo "GROUP(AS_NEEDED(\"%t\"))" > %t.script
 # RUN: ld.lld -o %t2 %t.script
 # RUN: llvm-readobj %t2 > /dev/null
 
+# CANNOT_OPEN: error: cannot open [[FILE]]: {{.*}}
+
 .globl _start
 _start:
   ret