[llvm-windres] Change the interpretation of --preprocessor to match Binutils 2.36

[mstorsjo]

Binutils 2.36 had a somewhat controversial change in how the --preprocessor option was handled in GNU windres; previously, the option was interpreted as a part of the command string, potentially containing multiple arguments (which even was hinted at in the documentation).

In Binutils 2.36, this was changed to interpret the --preprocessor argument as one argument (possibly containing spaces) pointing at the preprocessor executable.

The existing behaviour where implicit arguments like -E -xc -DRC_INVOKED are dropped if --preprocessor is specified, was kept.

This was a breaking change for some users of GNU windres, see https://sourceware.org/git/?p=binutils-gdb.git;a=commitdiff;h=21c33bcbe36377abf01614fb1b9be439a3b6de20, https://sourceware.org/bugzilla/show_bug.cgi?id=27594, and https://sourceware.org/git/?p=binutils-gdb.git;a=commitdiff;h=5edb8e3f5ad8d74a83fc0df7f6e4514eed0aa77f.

As multiple years have passed since, the behaviour change seems to be here to stay, and any users of the previous form of the option have been forced to avoid this construct. Thus update llvm-windres to match the new way Binutils of handling this option.

One construct for specifying the path to the preprocessor, which works both before and after binutils 2.36 (and this change in llvm-windres) is to specify options like this:

--preprocessor path/to/executable --preprocessor-arg -E --preprocessor-arg -xc -DRC_INVOKED

[llvmbot]

@llvm/pr-subscribers-platform-windows

Author: Martin Storsjö (mstorsjo)

Changes

Binutils 2.36 had a somewhat controversial change in how the --preprocessor option was handled in GNU windres; previously, the option was interpreted as a part of the command string, potentially containing multiple arguments (which even was hinted at in the documentation).

In Binutils 2.36, this was changed to interpret the --preprocessor argument as one argument (possibly containing spaces) pointing at the preprocessor executable.

The existing behaviour where implicit arguments like -E -xc -DRC_INVOKED are dropped if --preprocessor is specified, was kept.

This was a breaking change for some users of GNU windres, see https://sourceware.org/git/?p=binutils-gdb.git;a=commitdiff;h=21c33bcbe36377abf01614fb1b9be439a3b6de20, https://sourceware.org/bugzilla/show_bug.cgi?id=27594, and https://sourceware.org/git/?p=binutils-gdb.git;a=commitdiff;h=5edb8e3f5ad8d74a83fc0df7f6e4514eed0aa77f.

As multiple years have passed since, the behaviour change seems to be here to stay, and any users of the previous form of the option have been forced to avoid this construct. Thus update llvm-windres to match the new way Binutils of handling this option.

One construct for specifying the path to the preprocessor, which works both before and after binutils 2.36 (and this change in llvm-windres) is to specify options like this:

--preprocessor path/to/executable --preprocessor-arg -E --preprocessor-arg -xc -DRC_INVOKED

---

Full diff: https://github.com/llvm/llvm-project/pull/75391.diff

3 Files Affected:

• (modified) llvm/test/tools/llvm-rc/preproc.test (+1-1)
• (modified) llvm/test/tools/llvm-rc/windres-preproc.test (+22-3)
• (modified) llvm/tools/llvm-rc/llvm-rc.cpp (+22-43)

diff --git a/llvm/test/tools/llvm-rc/preproc.test b/llvm/test/tools/llvm-rc/preproc.test
index f55e5434dce360..7a6d8b3db03662 100644
--- a/llvm/test/tools/llvm-rc/preproc.test
+++ b/llvm/test/tools/llvm-rc/preproc.test
@@ -1,3 +1,3 @@
 ; RUN: llvm-rc -### -i%p "-DFOO1=\"foo bar\"" -UFOO2 -D FOO3 -- %p/Inputs/empty.rc | FileCheck %s
 
-; CHECK: {{^}} "clang" "--driver-mode=gcc" "-target" "{{.*}}-pc-windows-msvc-coff" "-E" "-xc" "-DRC_INVOKED" "{{.*}}empty.rc" "-o" "{{.*}}preproc-{{.*}}.rc" "-I" "{{.*}}" "-D" "FOO1=\"foo bar\"" "-U" "FOO2" "-D" "FOO3"{{$}}
+; CHECK: {{^}} "clang" "--driver-mode=gcc" "-target" "{{.*}}-pc-windows-msvc-coff" "-E" "-xc" "-DRC_INVOKED" "-I" "{{.*}}" "-D" "FOO1=\"foo bar\"" "-U" "FOO2" "-D" "FOO3" "{{.*}}empty.rc" "-o" "{{.*}}preproc-{{.*}}.rc"{{$}}
diff --git a/llvm/test/tools/llvm-rc/windres-preproc.test b/llvm/test/tools/llvm-rc/windres-preproc.test
index e55195b3a4d280..13f82299a074bb 100644
--- a/llvm/test/tools/llvm-rc/windres-preproc.test
+++ b/llvm/test/tools/llvm-rc/windres-preproc.test
@@ -5,6 +5,25 @@
 
 ; RUN: llvm-windres -### --include-dir %p/incdir1 --include %p/incdir2 "-DFOO1=\\\"foo bar\\\"" -UFOO2 -D FOO3 --preprocessor-arg "-DFOO4=\\\"baz baz\\\"" -DFOO5=\"bar\" %p/Inputs/empty.rc %t.res | FileCheck %s --check-prefix=CHECK1
 ; RUN: llvm-windres -### --include-dir %p/incdir1 --include %p/incdir2 "-DFOO1=\"foo bar\"" -UFOO2 -D FOO3 --preprocessor-arg "-DFOO4=\"baz baz\"" "-DFOO5=bar" %p/Inputs/empty.rc %t.res --use-temp-file | FileCheck %s --check-prefix=CHECK1
-; CHECK1: {{^}} "clang" "--driver-mode=gcc" "-target" "{{.*}}-{{.*}}{{mingw32|windows-gnu}}" "-E" "-xc" "-DRC_INVOKED" "{{.*}}empty.rc" "-o" "{{.*}}preproc-{{.*}}.rc" "-I" "{{.*}}incdir1" "-I" "{{.*}}incdir2" "-D" "FOO1=\"foo bar\"" "-U" "FOO2" "-D" "FOO3" "-DFOO4=\"baz baz\"" "-D" "FOO5=bar"{{$}}
-; RUN: llvm-windres -### --preprocessor "i686-w64-mingw32-gcc -E -DFOO=\\\"foo\\ bar\\\"" %p/Inputs/empty.rc %t.res | FileCheck %s --check-prefix=CHECK2
-; CHECK2: {{^}} "i686-w64-mingw32-gcc" "-E" "-DFOO=\"foo bar\"" "{{.*}}empty.rc" "-o" "{{.*}}preproc-{{.*}}.rc"{{$}}
+; CHECK1: {{^}} "clang" "--driver-mode=gcc" "-target" "{{.*}}-{{.*}}{{mingw32|windows-gnu}}" "-E" "-xc" "-DRC_INVOKED" "-I" "{{.*}}incdir1" "-I" "{{.*}}incdir2" "-D" "FOO1=\"foo bar\"" "-U" "FOO2" "-D" "FOO3" "-DFOO4=\"baz baz\"" "-D" "FOO5=bar" "{{.*}}empty.rc" "-o" "{{.*}}preproc-{{.*}}.rc"{{$}}
+; RUN: llvm-windres -### --preprocessor "i686-w64-mingw32-gcc" --preprocessor-arg -E "-DFOO=\\\"foo bar\\\"" %p/Inputs/empty.rc %t.res | FileCheck %s --check-prefix=CHECK2
+; CHECK2: {{^}} "{{.*}}i686-w64-mingw32-gcc" "-E" "-D" "FOO=\"foo bar\"" "{{.*}}empty.rc" "-o" "{{.*}}preproc-{{.*}}.rc"{{$}}
+
+;; Test resolving the --preprocessor executable from PATH
+
+; RUN: rm -rf %t-bin/testbin
+; RUN: mkdir -p %t-bin/testbin
+; RUN: ln -s llvm-windres %t-bin/testbin/i686-w64-mingw32-gcc
+; RUN: env PATH=%t-bin/testbin llvm-windres -### --preprocessor i686-w64-mingw32-gcc --preprocessor-arg -E --preprocessor-arg -xc -DRC_INVOKED %p/Inputs/empty.rc %t.res | FileCheck %s --check-prefix=CHECK3
+; CHECK3: {{^}} "{{.*}}/testbin/i686-w64-mingw32-gcc" "-E" "-xc" "-D" "RC_INVOKED" "{{.*}}empty.rc" "-o" "{{.*}}preproc-{{.*}}.rc"{{$}}
+
+
+;; Test error messages when unable to execute the preprocessor.
+
+; RUN: not llvm-windres --preprocessor intentionally-missing-executable %p/Inputs/empty.rc %t.res 2>&1 | FileCheck %s --check-prefix=CHECK4
+; CHECK4: llvm-rc: Preprocessing failed: Executable "intentionally-missing-executable" doesn't exist!
+
+;; Test --preprocessor with an argument with spaces.
+
+; RUN: llvm-windres -### --preprocessor "path with spaces/gcc" %p/Inputs/empty.rc %t.res | FileCheck %s --check-prefix=CHECK5
+; CHECK5: {{^}} "path with spaces/gcc" "{{.*}}empty.rc" "-o" "{{.*}}preproc-{{.*}}.rc"{{$}}
diff --git a/llvm/tools/llvm-rc/llvm-rc.cpp b/llvm/tools/llvm-rc/llvm-rc.cpp
index b955347f2a8646..78ab96492acc75 100644
--- a/llvm/tools/llvm-rc/llvm-rc.cpp
+++ b/llvm/tools/llvm-rc/llvm-rc.cpp
@@ -209,7 +209,7 @@ struct RcOptions {
   bool Preprocess = true;
   bool PrintCmdAndExit = false;
   std::string Triple;
-  std::vector<std::string> PreprocessCmd;
+  std::optional<std::string> Preprocessor;
   std::vector<std::string> PreprocessArgs;
 
   std::string InputFile;
@@ -229,7 +229,7 @@ struct RcOptions {
 void preprocess(StringRef Src, StringRef Dst, const RcOptions &Opts,
                 const char *Argv0) {
   std::string Clang;
-  if (Opts.PrintCmdAndExit || !Opts.PreprocessCmd.empty()) {
+  if (Opts.PrintCmdAndExit || Opts.Preprocessor) {
     Clang = "clang";
   } else {
     ErrorOr<std::string> ClangOrErr = findClang(Argv0, Opts.Triple);
@@ -248,16 +248,22 @@ void preprocess(StringRef Src, StringRef Dst, const RcOptions &Opts,
   SmallVector<StringRef, 8> Args = {
       Clang, "--driver-mode=gcc", "-target", Opts.Triple, "-E",
       "-xc", "-DRC_INVOKED"};
-  if (!Opts.PreprocessCmd.empty()) {
+  std::string PreprocessorExecutable;
+  if (Opts.Preprocessor) {
     Args.clear();
-    for (const auto &S : Opts.PreprocessCmd)
-      Args.push_back(S);
+    Args.push_back(*Opts.Preprocessor);
+    if (!sys::fs::can_execute(Args[0])) {
+      if (auto P = sys::findProgramByName(Args[0])) {
+        PreprocessorExecutable = *P;
+        Args[0] = PreprocessorExecutable;
+      }
+    }
   }
+  for (const auto &S : Opts.PreprocessArgs)
+    Args.push_back(S);
   Args.push_back(Src);
   Args.push_back("-o");
   Args.push_back(Dst);
-  for (const auto &S : Opts.PreprocessArgs)
-    Args.push_back(S);
   if (Opts.PrintCmdAndExit || Opts.BeVerbose) {
     for (const auto &A : Args) {
       outs() << " ";
@@ -269,9 +275,15 @@ void preprocess(StringRef Src, StringRef Dst, const RcOptions &Opts,
   }
   // The llvm Support classes don't handle reading from stdout of a child
   // process; otherwise we could avoid using a temp file.
-  int Res = sys::ExecuteAndWait(Args[0], Args);
+  std::string ErrMsg;
+  int Res =
+      sys::ExecuteAndWait(Args[0], Args, /*Env=*/std::nullopt, /*Redirects=*/{},
+                          /*SecondsToWait=*/0, /*MemoryLimit=*/0, &ErrMsg);
   if (Res) {
-    fatalError("llvm-rc: Preprocessing failed.");
+    if (!ErrMsg.empty())
+      fatalError("llvm-rc: Preprocessing failed: " + ErrMsg);
+    else
+      fatalError("llvm-rc: Preprocessing failed.");
   }
 }
 
@@ -329,36 +341,6 @@ std::string unescape(StringRef S) {
   return Out;
 }
 
-std::vector<std::string> unescapeSplit(StringRef S) {
-  std::vector<std::string> OutArgs;
-  std::string Out;
-  bool InQuote = false;
-  for (int I = 0, E = S.size(); I < E; I++) {
-    if (S[I] == '\\') {
-      if (I + 1 < E)
-        Out.push_back(S[++I]);
-      else
-        fatalError("Unterminated escape");
-      continue;
-    }
-    if (S[I] == '"') {
-      InQuote = !InQuote;
-      continue;
-    }
-    if (S[I] == ' ' && !InQuote) {
-      OutArgs.push_back(Out);
-      Out.clear();
-      continue;
-    }
-    Out.push_back(S[I]);
-  }
-  if (InQuote)
-    fatalError("Unterminated quote");
-  if (!Out.empty())
-    OutArgs.push_back(Out);
-  return OutArgs;
-}
-
 RcOptions parseWindresOptions(ArrayRef<const char *> ArgsArr,
                               ArrayRef<const char *> InputArgsArray,
                               std::string Prefix) {
@@ -493,11 +475,8 @@ RcOptions parseWindresOptions(ArrayRef<const char *> ArgsArr,
       break;
     }
   }
-  // TODO: If --use-temp-file is set, we shouldn't be unescaping
-  // the --preprocessor argument either, only splitting it.
   if (InputArgs.hasArg(WINDRES_preprocessor))
-    Opts.PreprocessCmd =
-        unescapeSplit(InputArgs.getLastArgValue(WINDRES_preprocessor));
+    Opts.Preprocessor = InputArgs.getLastArgValue(WINDRES_preprocessor);
 
   Opts.Params.CodePage = CpWin1252; // Different default
   if (InputArgs.hasArg(WINDRES_codepage)) {

[mstorsjo]

This goes on top of #75390 - only the topmost commmit should be reviewed in this PR.

CC @mati865 @lazka @pbo-linaro