Fix an assertion when -print-prog-name=

[chrib]

Summary

Fix an assertion when -print-prog-name= is invoked without parameter. Returns an empty string.

no test provided, as "obvious"

[compnerd]

I'm torn on this. The other -print options will perform the validation implicitly at the higher level before calling the inner functions. It is certainly reasonable to support that, but, for the common path, this check seems unnecessary (and this function is used elsewhere in clang). There is a similar problem that exists with -print-file-name=. We should probably fix both at the same time. Can you also please add a test case for this?

[chrib]

Move the non-null name check out of GetProgramPath and add a test case.

Assume that we trust the callers to check for non null ProgramName.

[chrib]

Hi Saleem,

Thanks for your review. I have amended the patch to avoid checking the name on the common path.
About your second comment, I'm not sure we have to fix -print-file-name= for an equivalent problem since in case of empty parameter, we do a concatenation with the driver's path, which seems to be fine.
Best Regards
Christian

[compnerd]

Do you have commit access or do you need someone to commit this on your behalf?

[chrib]

In D45814#1081203, @compnerd wrote:

Do you have commit access or do you need someone to commit this on your behalf?

can you commit it for me please ? thanks.

[compnerd]

SVN r331296

lib/Driver/Driver.cpp

bool Driver::HandleImmediateArgs(const Compilation &C) {
   // FIXME: The following handlers should use a callback mechanism, we don't
   // know what the client would like to do.
   if (Arg *A = C.getArgs().getLastArg(options::OPT_print_file_name_EQ)) {
     llvm::outs() << GetFilePath(A->getValue(), TC) << "\n";
     return false;
   }
 
   if (Arg *A = C.getArgs().getLastArg(options::OPT_print_prog_name_EQ)) {
-    llvm::outs() << GetProgramPath(A->getValue(), TC) << "\n";
+    StringRef ProgName = A->getValue();
+
+    // Null program name cannot have a path.
+    if (! ProgName.empty())
+      llvm::outs() << GetProgramPath(ProgName, TC);
+
+    llvm::outs() << "\n";
     return false;
   }
 
   if (Arg *A = C.getArgs().getLastArg(options::OPT_autocomplete)) {
     StringRef PassedFlags = A->getValue();
     HandleAutocompletions(PassedFlags);
     return false;
   }
for (const auto &Name : Names) {
     if (llvm::sys::fs::can_execute(Twine(Dir)))
       return true;
     llvm::sys::path::remove_filename(Dir);
   }
   return false;
 }
 
 std::string Driver::GetProgramPath(StringRef Name, const ToolChain &TC) const {
+
   SmallVector<std::string, 2> TargetSpecificExecutables;
   generatePrefixedToolNames(Name, TC, TargetSpecificExecutables);
 
   // Respect a limited subset of the '-Bprefix' functionality in GCC by
   // attempting to use this prefix when looking for program paths.
   for (const auto &PrefixDir : PrefixDirs) {
     if (llvm::sys::fs::is_directory(PrefixDir)) {
       SmallString<128> P(PrefixDir);

test/Driver/print-empty-prog-name.c

+// Test that -print-prog-name= correctly returns an empty string
+
+// RUN: %clang -print-prog-name= 2>&1 | FileCheck %s
+// CHECK-NOT:{{.+}}
+