Fix compilers seeing empty input due to file system races (#4708).

Changes

@@ -34,6 +34,7 @@ Verilator 5.019 devel
 * Fix MingW compilation (#4675). [David Ledger]
 * Fix trace when using SystemC with certain configurations (#4676). [Anthony Donlon]
 * Fix C++20 compilation errors (#4670).
+* Fix compilers seeing empty input due to file system races (#4708). [Flavien Solt]
 
 
 Verilator 5.018 2023-10-30

src/V3File.cpp

@@ -191,7 +191,7 @@ void V3FileDependImp::writeTimes(const string& filename, const string& cmdlineIn
         // Read stats of files we create after we're done making them
         // (except for this file, of course)
         DependFile* const dfp = const_cast<DependFile*>(&(*iter));
-        V3Options::fileNfsFlush(dfp->filename());
+        V3Os::filesystemFlush(dfp->filename());
         dfp->loadStats();
         off_t showSize = iter->size();
         ino_t showIno = iter->ino();
@@ -256,7 +256,7 @@ bool V3FileDependImp::checkTimes(const string& filename, const string& cmdlineIn
         *ifp >> quote;
         const string chkFilename = V3Os::getline(*ifp, '"');
 
-        V3Options::fileNfsFlush(chkFilename);
+        V3Os::filesystemFlush(chkFilename);
         // NOLINTNEXTLINE(cppcoreguidelines-pro-type-member-init)
         struct stat chkStat;
         const int err = stat(chkFilename.c_str(), &chkStat);

src/V3Options.cpp

@@ -456,23 +456,6 @@ bool V3Options::fileStatNormal(const string& filename) {
     return true;
 }
 
-void V3Options::fileNfsFlush(const string& filename) {
-    // NFS caches stat() calls so to get up-to-date information must
-    // do a open or opendir on the filename.
-    // Faster to just try both rather than check if a file is a dir.
-#ifdef _MSC_VER
-    if (int fd = ::open(filename.c_str(), O_RDONLY)) {  // LCOV_EXCL_BR_LINE
-        if (fd > 0) ::close(fd);
-    }
-#else
-    if (DIR* const dirp = opendir(filename.c_str())) {  // LCOV_EXCL_BR_LINE
-        closedir(dirp);  // LCOV_EXCL_LINE
-    } else if (int fd = ::open(filename.c_str(), O_RDONLY)) {  // LCOV_EXCL_BR_LINE
-        if (fd > 0) ::close(fd);
-    }
-#endif
-}
-
 string V3Options::fileExists(const string& filename) {
     // Surprisingly, for VCS and other simulators, this process
     // is quite slow; presumably because of re-reading each directory

src/V3Options.h

@@ -697,7 +697,6 @@ public:
     void filePathLookedMsg(FileLine* fl, const string& modname);
     V3LangCode fileLanguage(const string& filename);
     static bool fileStatNormal(const string& filename);
-    static void fileNfsFlush(const string& filename);
 
     // METHODS (other OS)
     static void throwSigsegv();

src/V3Os.cpp

@@ -45,6 +45,7 @@ VL_DEFINE_DEBUG_FUNCTIONS;
 #define PATH_MAX MAX_PATH
 #else
 #include <dirent.h>
+#include <utime.h>
 #endif
 #include <fstream>
 #include <memory>
@@ -58,6 +59,7 @@ VL_DEFINE_DEBUG_FUNCTIONS;
 # include <bcrypt.h>  // BCryptGenRandom
 # include <chrono>
 # include <direct.h>  // mkdir
+# include <io.h>  // open, read, write, close
 # include <psapi.h>   // GetProcessMemoryInfo
 # include <thread>
 // These macros taken from gdbsupport/gdb_wait.h in binutils-gdb
@@ -74,6 +76,7 @@ VL_DEFINE_DEBUG_FUNCTIONS;
 # include <sys/time.h>
 # include <sys/wait.h>  // Needed on FreeBSD for WIFEXITED
 # include <unistd.h>  // usleep
+# include <fcntl.h>
 #endif
 // clang-format on
 
@@ -294,6 +297,31 @@ void V3Os::createDir(const string& dirname) {
 #endif
 }
 
+void V3Os::filesystemFlush(const string& dirname) {
+    // NFS caches stat() calls so to get up-to-date information must
+    // do a open or opendir on the filename.
+#ifdef _MSC_VER
+    if (int fd = ::open(filename.c_str(), O_RDONLY)) {  // LCOV_EXCL_BR_LINE
+        if (fd > 0) ::close(fd);
+    }
+#else
+    {
+        // Linux kernel may not reread from NFS unless timestamp modified
+        struct timeval tv;
+        gettimeofday(&tv, NULL);
+        const int err = utimes(dirname.c_str(), &tv);
+        // Not an error
+        if (err != 0) UINFO(1, "-Info: File not statable: " << dirname << endl);
+    }
+    // Faster to just try both rather than check if a file is a dir.
+    if (DIR* const dirp = opendir(dirname.c_str())) {  // LCOV_EXCL_BR_LINE
+        closedir(dirp);  // LCOV_EXCL_LINE
+    } else if (int fd = ::open(dirname.c_str(), O_RDONLY)) {  // LCOV_EXCL_BR_LINE
+        if (fd > 0) ::close(fd);
+    }
+#endif
+}
+
 void V3Os::unlinkRegexp(const string& dir, const string& regexp) {
 #ifdef _MSC_VER
     try {

src/V3Os.h

@@ -63,6 +63,7 @@ public:
 
     // METHODS (directory utilities)
     static void createDir(const string& dirname);
+    static void filesystemFlush(const string& dirname);
     static void unlinkRegexp(const string& dir, const string& regexp);
 
     // METHODS (random)

src/Verilator.cpp

@@ -636,9 +636,12 @@ static void verilate(const string& argString) {
     // --FRONTEND------------------
 
     // Cleanup
-    V3Os::unlinkRegexp(v3Global.opt.hierTopDataDir(), v3Global.opt.prefix() + "_*.tree");
+    // Ideally we'd do prefix + "_*.*", and prefix + ".*", but this seems
+    // potentially disruptive to old behavior
     V3Os::unlinkRegexp(v3Global.opt.hierTopDataDir(), v3Global.opt.prefix() + "_*.dot");
+    V3Os::unlinkRegexp(v3Global.opt.hierTopDataDir(), v3Global.opt.prefix() + "_*.tree");
     V3Os::unlinkRegexp(v3Global.opt.hierTopDataDir(), v3Global.opt.prefix() + "_*.txt");
+    V3Os::unlinkRegexp(v3Global.opt.hierTopDataDir(), v3Global.opt.prefix() + "_*_DepSet_*");
 
     // Internal tests (after option parsing as need debug() setting,
     // and after removing files as may make debug output)
@@ -717,6 +720,9 @@ static void verilate(const string& argString) {
                            argString);
     }
 
+    V3Os::filesystemFlush(v3Global.opt.makeDir());
+    if (v3Global.opt.hierTop()) V3Os::filesystemFlush(v3Global.opt.hierTopDataDir());
+
     // Final writing shouldn't throw warnings, but...
     V3Error::abortIfWarnings();
 }
@@ -747,6 +753,7 @@ static void execBuildJob() {
     UINFO(1, "Start Build\n");
 
     const string cmdStr = buildMakeCmd(v3Global.opt.prefix() + ".mk", "");
+    V3Os::filesystemFlush(v3Global.opt.hierTopDataDir());
     const int exit_code = V3Os::system(cmdStr);
     if (exit_code != 0) {
         v3error(cmdStr << " exited with " << exit_code << std::endl);
@@ -759,6 +766,7 @@ static void execHierVerilation() {
     const string makefile = v3Global.opt.prefix() + "_hier.mk ";
     const string target = v3Global.opt.build() ? " hier_build" : " hier_verilation";
     const string cmdStr = buildMakeCmd(makefile, target);
+    V3Os::filesystemFlush(v3Global.opt.hierTopDataDir());
     const int exit_code = V3Os::system(cmdStr);
     if (exit_code != 0) {
         v3error(cmdStr << " exited with " << exit_code << std::endl);