[PDB] Don't include input files in the 'cmd' entry of S_ENVBLOCK

[saudi]

Summary

The S_ENVBLOCK is used for the Linker information inside of the pdb file contains an entry "cmd" for the command line arguments.
This patch aligns this entry to what MSVC generates, stripping the input files arguments.

The issue we encountered was in the case of a large project where we link many .obj files, and trying to use the Live++ tool for edit-and-continue.
Since the linker's command line reached 100KB, it gets truncated to match the 64 KB limit of the S_ENVBLOCK of the PDB file.
Live++ uses it to detect whether the appropriate flags (like /FUNCTIONPADMIN) were used for proper hotpatching.
It may miss truncated arguments and give false warnings to the user.

In our case, with this patch, the 100KB command line (which tends to get bigger as the project evolves) gets reduced to about 12KB, and evolves much slower.

Pros:

• align on MSVC's behavior
• keep S_ENVBLOCK size under the 64KB limit

Cons:

• the command line found in the pdb can't be used as-is to link the project the way it was.

[saudi]

Added release note

[thakis]

lld/COFF/PDB.cpp

1357

What if I'm cross-linking on Linux and passing in /path/to/foo.o?

[saudi]

lld/COFF/PDB.cpp

1357

Indeed, I can't make the assumption that any argument starting with / is an input file.
I'll investigate more to get a posix-friendly version.

[saudi]

Perform the argument list filtering in the driver, to use the result of parsed arguments.
Updated pdb-linker-module.test, checking that the object file is indeed discarded.

Since the object file is provided as an absolute path, this checks that '/path/to/file.o' is not mistaken for a command line argument.

[thakis]

Works for me, thanks!

lld/COFF/DriverUtils.cpp

859 ↗

(On Diff #474593)

Instead of this line, maybe config->argv.push_back(argv[0]);? Maybe a bit more direct.

[saudi]

Simplified init of config->argv

[saudi]

lld/COFF/DriverUtils.cpp

859 ↗

(On Diff #474593)

replacing with = {argv[0]} to keep the previous behavior concerning re-initialization of config->argv

[thieta]

LGTM!

lld/COFF/PDB.cpp

static codeview::CPUType toCodeViewMachine(COFF::MachineTypes machine) {
   default:
     llvm_unreachable("Unsupported CPU Type");
   }
 }
 
 // Mimic MSVC which surrounds arguments containing whitespace with quotes.
 // Double double-quotes are handled, so that the resulting string can be
 // executed again on the cmd-line.
-static std::string quote(ArrayRef<StringRef> args) {
+// Also, MSVC discards input file arguments (not prefixed with "/" or "-").
+// It avoids reaching the size limit for S_ENVBLOCK in most scenarios.
+static std::string makeArgString(ArrayRef<StringRef> args) {
   std::string r;
   r.reserve(256);
   for (StringRef a : args) {
+    if (!a.startswith("/") && !a.startswith("-"))
+      continue;
     if (!r.empty())
       r.push_back(' ');
     bool hasWS = a.contains(' ');
     bool hasQ = a.contains('"');
     if (hasWS || hasQ)
       r.push_back('"');
     if (hasQ) {
       SmallVector<StringRef, 4> s;
static void addCommonLinkerModuleSymbols(StringRef path,
   EnvBlockSym ebs(SymbolRecordKind::EnvBlockSym);
   Compile3Sym cs(SymbolRecordKind::Compile3Sym);
   fillLinkerVerRecord(cs);
 
   ons.Name = "* Linker *";
   ons.Signature = 0;
 
   ArrayRef<StringRef> args = makeArrayRef(config->argv).drop_front();
-  std::string argStr = quote(args);
+  std::string argStr = makeArgString(args);
   ebs.Fields.push_back("cwd");
   SmallString<64> cwd;
   if (config->pdbSourcePath.empty())
     sys::fs::current_path(cwd);
   else
     cwd = config->pdbSourcePath;
   ebs.Fields.push_back(cwd);
   ebs.Fields.push_back("exe");

lld/test/COFF/pdb-linker-module.test

 SYMS-NEXT: 64 | S_ENVBLOCK
 SYMS-NEXT: - cwd
 SYMS-NEXT: -
 SYMS-NEXT: - exe
 SYMS-NEXT: - {{.*}}lld-link
 SYMS-NEXT: - pdb
 SYMS-NEXT: - {{.*}}pdb-linker-module{{.*}}pdb
 SYMS-NEXT: - cmd
-SYMS-NEXT: - /debug /pdb:{{.*}}pdb-linker-module{{.*}}pdb /nodefaultlib "/entry:1 ""hello"" 2" "/manifestuac:level='asInvoker' uiAccess='false'" {{.*}}pdb-diff.obj
+SYMS-NEXT: - /debug /pdb:{{.*}}pdb-linker-module{{.*}}pdb /nodefaultlib "/entry:1 ""hello"" 2" "/manifestuac:level='asInvoker' uiAccess='false'"

lld/test/COFF/pdb-relative-source-lines.test

 CHECK-NEXT:       Entries:     
 CHECK-NEXT:         - cwd
 CHECK-NEXT:         - 'c:\src'
 CHECK-NEXT:         - exe
 CHECK-NEXT:         - 'c:\src\lld-link'
 CHECK-NEXT:         - pdb 
 CHECK-NEXT:         - 'c:\src\out.pdb'
 CHECK-NEXT:         - cmd
-CHECK-NEXT:         - '-debug -pdbsourcepath:c:\src -entry:main -nodefaultlib -out:out.exe -pdb:out.pdb pdb_lines_1_relative.obj pdb_lines_2_relative.obj'
+CHECK-NEXT:         - '-debug -pdbsourcepath:c:\src -entry:main -nodefaultlib -out:out.exe -pdb:out.pdb'
 
 CHECK-LABEL: IpiStream:
 
 CHECK:    - Kind:            LF_STRING_ID
 CHECK-NEXT:      StringId:
 CHECK-NEXT:        Id:              0
 CHECK-NEXT:        String:          .
 CHECK-NEXT:     - Kind:            LF_STRING_ID

 POSIX-NEXT:       Entries:     
 POSIX-NEXT:         - cwd
 POSIX-NEXT:         - '/usr/src'
 POSIX-NEXT:         - exe
 POSIX-NEXT:         - '/usr/src/lld-link'
 POSIX-NEXT:         - pdb 
 POSIX-NEXT:         - '/usr/src/out.pdb'
 POSIX-NEXT:         - cmd
-POSIX-NEXT:         - '-debug -pdbsourcepath:/usr/src -entry:main -nodefaultlib -out:out.exe -pdb:out.pdb pdb_lines_1_relative.obj pdb_lines_2_relative.obj'
+POSIX-NEXT:         - '-debug -pdbsourcepath:/usr/src -entry:main -nodefaultlib -out:out.exe -pdb:out.pdb'
 
 ABSOLUTE-LABEL: StringTable:
 ABSOLUTE-NOT: {{/|\\}}.{{/|\\}}pdb_lines_1.c
 
 POSIX-LABEL: IpiStream:
 POSIX:    - Kind:            LF_STRING_ID
 POSIX-NEXT:      StringId:
 POSIX-NEXT:        Id:              0