diff --git a/programs/fileio.c b/programs/fileio.c
index 7666b0725..d4aea1591 100644
--- a/programs/fileio.c
+++ b/programs/fileio.c
@@ -270,9 +270,9 @@ void FIO_addAbortHandler()
 static FIO_compressionType_t g_compressionType = FIO_zstdCompression;
 void FIO_setCompressionType(FIO_compressionType_t compressionType) { g_compressionType = compressionType; }
 static U32 g_overwrite = 0;
-void FIO_overwriteMode(void) { g_overwrite=1; }
-static U32 g_sparseFileSupport = 1;   /* 0: no sparse allowed; 1: auto (file yes, stdout no); 2: force sparse */
-void FIO_setSparseWrite(unsigned sparse) { g_sparseFileSupport=sparse; }
+void FIO_overwriteMode(void) { g_overwrite = 1; }
+static U32 g_sparseFileSupport = ZSTD_SPARSE_DEFAULT;   /* 0: no sparse allowed; 1: auto (file yes, stdout no); 2: force sparse */
+void FIO_setSparseWrite(unsigned sparse) { g_sparseFileSupport = sparse; }
 static U32 g_dictIDFlag = 1;
 void FIO_setDictIDFlag(unsigned dictIDFlag) { g_dictIDFlag = dictIDFlag; }
 static U32 g_checksumFlag = 1;
@@ -416,23 +416,23 @@ static FILE* FIO_openDstFile(const char* srcFileName, const char* dstFileName)
     if (!strcmp (dstFileName, stdoutmark)) {
         DISPLAYLEVEL(4,"Using stdout for output \n");
         SET_BINARY_MODE(stdout);
-        if (g_sparseFileSupport==1) {
+        if (g_sparseFileSupport == 1) {
             g_sparseFileSupport = 0;
             DISPLAYLEVEL(4, "Sparse File Support is automatically disabled on stdout ; try --sparse \n");
         }
         return stdout;
     }
+
     if (srcFileName != NULL) {
         stat_t srcStat;
         stat_t dstStat;
         if ( UTIL_getFileStat(srcFileName, &srcStat)
-          && UTIL_getFileStat(dstFileName, &dstStat)
-          && srcStat.st_dev == dstStat.st_dev
-          && srcStat.st_ino == dstStat.st_ino ) {
-            DISPLAYLEVEL(1, "zstd: Refusing to open a output file which will overwrite the input file \n");
-            return NULL;
-        }
-    }
+          && UTIL_getFileStat(dstFileName, &dstStat) ) {
+            if ( srcStat.st_dev == dstStat.st_dev
+              && srcStat.st_ino == dstStat.st_ino ) {
+                DISPLAYLEVEL(1, "zstd: Refusing to open a output file which will overwrite the input file \n");
+                return NULL;
+    }   }   }
 
     if (g_sparseFileSupport == 1) {
         g_sparseFileSupport = ZSTD_SPARSE_DEFAULT;
@@ -1440,12 +1440,14 @@ static unsigned FIO_fwriteSparse(FILE* file, const void* buffer, size_t bufferSi
 
 static void FIO_fwriteSparseEnd(FILE* file, unsigned storedSkips)
 {
-    if (storedSkips-->0) {   /* implies g_sparseFileSupport>0 */
-        int const seekResult = LONG_SEEK(file, storedSkips, SEEK_CUR);
-        if (seekResult != 0) EXM_THROW(69, "Final skip error (sparse file)");
+    if (storedSkips>0) {
+        assert(g_sparseFileSupport > 0);  /* storedSkips>0 implies sparse support is enabled */
+        if (LONG_SEEK(file, storedSkips-1, SEEK_CUR) != 0)
+            EXM_THROW(69, "Final skip error (sparse file support)");
+        /* last zero must be explicitly written,
+         * so that skipped ones get implicitly translated as zero by FS */
         {   const char lastZeroByte[1] = { 0 };
-            size_t const sizeCheck = fwrite(lastZeroByte, 1, 1, file);
-            if (sizeCheck != 1)
+            if (fwrite(lastZeroByte, 1, 1, file) != 1)
                 EXM_THROW(69, "Write error : cannot write last zero");
     }   }
 }
diff --git a/programs/util.c b/programs/util.c
index 4ef988c26..00fc4fe2c 100644
--- a/programs/util.c
+++ b/programs/util.c
@@ -18,6 +18,7 @@ extern "C" {
 ******************************************/
 #include <string.h>       /* strncmp */
 #include <errno.h>
+#include <assert.h>
 
 #include "util.h"
 
@@ -175,21 +176,23 @@ int UTIL_prepareFileList(const char *dirName, char** bufStart, size_t* pos, char
         pathLength = dirLength+1+fnameLength;
         path[pathLength] = 0;
         if (cFile.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY) {
-            if (strcmp (cFile.cFileName, "..") == 0 ||
-                strcmp (cFile.cFileName, ".") == 0) continue;
-
-            nbFiles += UTIL_prepareFileList(path, bufStart, pos, bufEnd, followLinks);  /* Recursively call "UTIL_prepareFileList" with the new path. */
+            if ( strcmp (cFile.cFileName, "..") == 0
+              || strcmp (cFile.cFileName, ".") == 0 )
+                continue;
+            /* Recursively call "UTIL_prepareFileList" with the new path. */
+            nbFiles += UTIL_prepareFileList(path, bufStart, pos, bufEnd, followLinks);
             if (*bufStart == NULL) { free(path); FindClose(hFile); return 0; }
-        }
-        else if ((cFile.dwFileAttributes & FILE_ATTRIBUTE_NORMAL) || (cFile.dwFileAttributes & FILE_ATTRIBUTE_ARCHIVE) || (cFile.dwFileAttributes & FILE_ATTRIBUTE_COMPRESSED)) {
+        } else if ( (cFile.dwFileAttributes & FILE_ATTRIBUTE_NORMAL)
+                 || (cFile.dwFileAttributes & FILE_ATTRIBUTE_ARCHIVE)
+                 || (cFile.dwFileAttributes & FILE_ATTRIBUTE_COMPRESSED) ) {
             if (*bufStart + *pos + pathLength >= *bufEnd) {
-                ptrdiff_t newListSize = (*bufEnd - *bufStart) + LIST_SIZE_INCREASE;
+                ptrdiff_t const newListSize = (*bufEnd - *bufStart) + LIST_SIZE_INCREASE;
                 *bufStart = (char*)UTIL_realloc(*bufStart, newListSize);
-                *bufEnd = *bufStart + newListSize;
                 if (*bufStart == NULL) { free(path); FindClose(hFile); return 0; }
+                *bufEnd = *bufStart + newListSize;
             }
             if (*bufStart + *pos + pathLength < *bufEnd) {
-                strncpy(*bufStart + *pos, path, *bufEnd - (*bufStart + *pos));
+                memcpy(*bufStart + *pos, path, pathLength+1 /* include final \0 */);
                 *pos += pathLength + 1;
                 nbFiles++;
             }
@@ -246,7 +249,7 @@ int UTIL_prepareFileList(const char *dirName, char** bufStart, size_t* pos, char
                 if (*bufStart == NULL) { free(path); closedir(dir); return 0; }
             }
             if (*bufStart + *pos + pathLength < *bufEnd) {
-                strncpy(*bufStart + *pos, path, *bufEnd - (*bufStart + *pos));
+                memcpy(*bufStart + *pos, path, pathLength + 1);  /* with final \0 */
                 *pos += pathLength + 1;
                 nbFiles++;
             }
@@ -304,7 +307,7 @@ UTIL_createFileList(const char **inputNames, unsigned inputNamesNb,
                 if (!buf) return NULL;
             }
             if (buf + pos + len < bufend) {
-                strncpy(buf + pos, inputNames[i], bufend - (buf + pos));
+                memcpy(buf+pos, inputNames[i], len+1);  /* with final \0 */
                 pos += len + 1;
                 nbFiles++;
             }
@@ -336,6 +339,7 @@ UTIL_createFileList(const char **inputNames, unsigned inputNamesNb,
 ******************************************/
 int g_utilDisplayLevel;
 
+
 /*-****************************************
 *  Time functions
 ******************************************/
@@ -354,6 +358,7 @@ U64 UTIL_getSpanTimeMicro(UTIL_time_t clockStart, UTIL_time_t clockEnd)
     }
     return 1000000ULL*(clockEnd.QuadPart - clockStart.QuadPart)/ticksPerSecond.QuadPart;
 }
+
 U64 UTIL_getSpanTimeNano(UTIL_time_t clockStart, UTIL_time_t clockEnd)
 {
     static LARGE_INTEGER ticksPerSecond;
@@ -367,7 +372,9 @@ U64 UTIL_getSpanTimeNano(UTIL_time_t clockStart, UTIL_time_t clockEnd)
 }
 
 #elif defined(__APPLE__) && defined(__MACH__)
+
 UTIL_time_t UTIL_getTime(void) { return mach_absolute_time(); }
+
 U64 UTIL_getSpanTimeMicro(UTIL_time_t clockStart, UTIL_time_t clockEnd)
 {
     static mach_timebase_info_data_t rate;
@@ -436,11 +443,13 @@ U64 UTIL_getSpanTimeNano(UTIL_time_t begin, UTIL_time_t end)
 }
 
 #else   /* relies on standard C (note : clock_t measurements can be wrong when using multi-threading) */
+
 typedef clock_t UTIL_time_t;
 #define UTIL_TIME_INITIALIZER 0
 UTIL_time_t UTIL_getTime(void) { return clock(); }
 U64 UTIL_getSpanTimeMicro(UTIL_time_t clockStart, UTIL_time_t clockEnd) { return 1000000ULL * (clockEnd - clockStart) / CLOCKS_PER_SEC; }
 U64 UTIL_getSpanTimeNano(UTIL_time_t clockStart, UTIL_time_t clockEnd) { return 1000000000ULL * (clockEnd - clockStart) / CLOCKS_PER_SEC; }
+
 #endif
 
 /* returns time span in microseconds */
diff --git a/tests/playTests.sh b/tests/playTests.sh
index fc45ef5ec..94a70458c 100755
--- a/tests/playTests.sh
+++ b/tests/playTests.sh
@@ -184,9 +184,9 @@ $ZSTD tmpro -c --no-progress | $ZSTD -d -o "$INTOVOID" --no-progress
 $ZSTD tmpro -cv --no-progress | $ZSTD -dv -o "$INTOVOID" --no-progress
 rm -f tmpro tmpro.zst
 $ECHO "test: overwrite input file (must fail)"
-$ZSTD tmp -fo tmp && die "zstd overwrote the input file"
-$ZSTD tmp.zst -dfo tmp.zst && die "zstd overwrote the input file"
-$ECHO "test: properly detect input file does not exist"
+$ZSTD tmp -fo tmp && die "zstd compression overwrote the input file"
+$ZSTD tmp.zst -dfo tmp.zst && die "zstd decompression overwrote the input file"
+$ECHO "test: detect that input file does not exist"
 $ZSTD nothere && die "zstd hasn't detected that input file does not exist"
 
 $ECHO "test : file removal"