[#5152] Write preprocessed P4 to <program_name>.p4pp file when --save-temps option is provided

frontends/common/parser_options.cpp

@@ -24,8 +24,10 @@ limitations under the License.
 #include <sys/wait.h>
 
 #include <filesystem>
+#include <fstream>
 #include <memory>
 #include <regex>
+#include <sstream>
 #include <unordered_set>
 
 #include "absl/strings/escaping.h"
@@ -121,6 +123,13 @@ ParserOptions::ParserOptions(std::string_view defaultMessage) : Util::Options(de
             return true;
         },
         "Output `make` dependency rule only (passed to preprocessor)");
+    registerOption(
+        "--save-temps", nullptr,
+        [this](const char *) {
+            savePreprocessed = true;
+            return true;
+        },
+        "Saves preprocessed P4 to filename.p4pp and do not exit compilation.");
     registerOption(
         "-MD", nullptr,
         [this](const char *) {
@@ -405,16 +414,28 @@ const char *ParserOptions::getIncludePath() const {
     return path.c_str();
 }
 
+// From (folder, file.ext, suffix)  returns
+// folder/file-suffix.ext
+static std::filesystem::path makeFileName(const std::filesystem::path &folder,
+                                          const std::filesystem::path &name,
+                                          std::string_view baseSuffix) {
+    std::filesystem::path newName(name.stem());
+    newName += baseSuffix;
+    newName += name.extension();
+
+    return folder / newName;
+}
+
 std::optional<ParserOptions::PreprocessorResult> ParserOptions::preprocess() const {
     FILE *in = nullptr;
 
     if (file == "-") {
         in = stdin;
     } else {
 #ifdef __clang__
-        std::string cmd("cc -E -x c -Wno-comment");
+        std::string cmd = "cc -E -x c -Wno-comment";
 #else
-        std::string cmd("cpp");
+        std::string cmd = "cpp";
 #endif
 
         cmd += " -C -undef -nostdinc -x assembler-with-cpp " + preprocessor_options.string() +
@@ -439,19 +460,36 @@ std::optional<ParserOptions::PreprocessorResult> ParserOptions::preprocess() con
         }
         return std::nullopt;
     }
-    return ParserOptions::PreprocessorResult(in, &closeFile);
-}
 
-// From (folder, file.ext, suffix)  returns
-// folder/file-suffix.ext
-static std::filesystem::path makeFileName(const std::filesystem::path &folder,
-                                          const std::filesystem::path &name,
-                                          std::string_view baseSuffix) {
-    std::filesystem::path newName(name.stem());
-    newName += baseSuffix;
-    newName += name.extension();
+    if (savePreprocessed) {
+        std::stringstream stream;
+        char *line = nullptr;
+        size_t len = 0;
+        ssize_t read = 0;
 
-    return folder / newName;
+        while ((read = getline(&line, &len, in)) != -1) {
+            stream << line;
+        }
+        closeFile(in);
+
+        std::filesystem::path fileName(file.stem());
+        fileName += ".p4pp";
+        fileName = makeFileName(dumpFolder, fileName, "");
+        std::ofstream filestream{fileName};
+        if (filestream) {
+            if (Log::verbose()) std::cerr << "Writing preprocessed P4 to " << fileName << std::endl;
+            filestream << stream.str();
+        }
+        filestream.close();
+
+        in = fopen(fileName.c_str(), "r");
+        if (in == nullptr) {
+            ::P4::error(ErrorType::ERR_IO, "Error invoking preprocessor");
+            perror("");
+            return std::nullopt;
+        }
+    }
+    return ParserOptions::PreprocessorResult(in, &closeFile);
 }
 
 bool ParserOptions::isv1() const { return langVersion == ParserOptions::FrontendVersion::P4_14; }

frontends/common/parser_options.h

@@ -82,6 +82,8 @@ class ParserOptions : public Util::Options {
     std::filesystem::path file;
     /// if true preprocess only
     bool doNotCompile = false;
+    /// if true save preprocessed P4 to filename.p4pp
+    bool savePreprocessed = false;
     /// Compiler version.
     cstring compilerVersion;
     /// if true skip preprocess

testdata/p4_16_errors_outputs/issue4365_no_demote_error_to_info.p4-stderr

@@ -7,6 +7,7 @@
 -U arg                                  Undefine macro (passed to preprocessor)
 -E                                      Preprocess only, do not compile (prints program on stdout)
 -M                                      Output `make` dependency rule only (passed to preprocessor)
+--save-temps                            Saves preprocessed P4 to filename.p4pp and do not exit compilation.
 -MD                                     Output `make` dependency rule to file as side effect (passed to preprocessor)
 -MF file                                With -M, specify output file for dependencies (passed to preprocessor)
 -MG                                     with -M, suppress errors for missing headers (passed to preprocessor)

testdata/p4_16_errors_outputs/issue4365_no_demote_error_to_warning.p4-stderr

@@ -7,6 +7,7 @@
 -U arg                                  Undefine macro (passed to preprocessor)
 -E                                      Preprocess only, do not compile (prints program on stdout)
 -M                                      Output `make` dependency rule only (passed to preprocessor)
+--save-temps                            Saves preprocessed P4 to filename.p4pp and do not exit compilation.
 -MD                                     Output `make` dependency rule to file as side effect (passed to preprocessor)
 -MF file                                With -M, specify output file for dependencies (passed to preprocessor)
 -MG                                     with -M, suppress errors for missing headers (passed to preprocessor)

testdata/p4_16_errors_outputs/issue4365_no_disable_error.p4-stderr

@@ -7,6 +7,7 @@
 -U arg                                  Undefine macro (passed to preprocessor)
 -E                                      Preprocess only, do not compile (prints program on stdout)
 -M                                      Output `make` dependency rule only (passed to preprocessor)
+--save-temps                            Saves preprocessed P4 to filename.p4pp and do not exit compilation.
 -MD                                     Output `make` dependency rule to file as side effect (passed to preprocessor)
 -MF file                                With -M, specify output file for dependencies (passed to preprocessor)
 -MG                                     with -M, suppress errors for missing headers (passed to preprocessor)