diff --git a/libc/stdio/printf_common.h b/libc/stdio/printf_common.h
index 85c91de..9b7c329 100644
--- a/libc/stdio/printf_common.h
+++ b/libc/stdio/printf_common.h
@@ -535,7 +535,7 @@
    */
   if (tablemax >= STATIC_ARG_TBL_SIZE) {
     *argtablesiz = sizeof(union arg) * (tablemax + 1);
-    *argtable = static_cast<arg*>(mmap(NULL, *argtablesiz,
+    *argtable = static_cast<arg*>(mmap(nullptr, *argtablesiz,
                                        PROT_WRITE | PROT_READ,
                                        MAP_ANON | MAP_PRIVATE, -1, 0));
     if (*argtable == MAP_FAILED) return -1;
@@ -629,9 +629,9 @@
   ret = -1;
 
 finish:
-  if (typetable != NULL && typetable != stattypetable) {
+  if (typetable != nullptr && typetable != stattypetable) {
     munmap(typetable, *argtablesiz);
-    typetable = NULL;
+    typetable = nullptr;
   }
   return (ret);
 }
@@ -646,13 +646,13 @@
   if (new_size < getpagesize()) new_size = getpagesize();
 
   if (*tablesize == STATIC_ARG_TBL_SIZE) {
-    *typetable = static_cast<unsigned char*>(mmap(NULL, new_size,
+    *typetable = static_cast<unsigned char*>(mmap(nullptr, new_size,
                                                   PROT_WRITE | PROT_READ,
                                                   MAP_ANON | MAP_PRIVATE, -1, 0));
     if (*typetable == MAP_FAILED) return -1;
     bcopy(old_table, *typetable, *tablesize);
   } else {
-    unsigned char* new_table = static_cast<unsigned char*>(mmap(NULL, new_size,
+    unsigned char* new_table = static_cast<unsigned char*>(mmap(nullptr, new_size,
                                                                 PROT_WRITE | PROT_READ,
                                                                 MAP_ANON | MAP_PRIVATE, -1, 0));
     if (new_table == MAP_FAILED) return -1;
@@ -695,8 +695,8 @@
     if (prec < 0) {
       memset(&mbs, 0, sizeof(mbs));
       p = wcsarg;
-      nbytes = wcsrtombs(NULL, (const wchar_t**)&p, 0, &mbs);
-      if (nbytes == (size_t)-1) return NULL;
+      nbytes = wcsrtombs(nullptr, (const wchar_t**)&p, 0, &mbs);
+      if (nbytes == (size_t)-1) return nullptr;
     } else {
       // Optimisation: if the output precision is small enough,
       // just allocate enough memory for the maximum instead of
@@ -712,17 +712,17 @@
           if (clen == 0 || clen == (size_t)-1 || nbytes + clen > (size_t)prec) break;
           nbytes += clen;
         }
-        if (clen == (size_t)-1) return NULL;
+        if (clen == (size_t)-1) return nullptr;
       }
     }
-    if ((convbuf = static_cast<char*>(malloc(nbytes + 1))) == NULL) return NULL;
+    if ((convbuf = static_cast<char*>(malloc(nbytes + 1))) == nullptr) return nullptr;
 
     // Fill the output buffer.
     p = wcsarg;
     memset(&mbs, 0, sizeof(mbs));
     if ((nbytes = wcsrtombs(convbuf, (const wchar_t**)&p, nbytes, &mbs)) == (size_t)-1) {
       free(convbuf);
-      return NULL;
+      return nullptr;
     }
     convbuf[nbytes] = '\0';
     return convbuf;
@@ -764,7 +764,7 @@
     const char* p;
     size_t insize, nchars, nconv;
 
-    if (mbsarg == NULL) return NULL;
+    if (mbsarg == nullptr) return nullptr;
 
     // Supplied argument is a multibyte string; convert it to wide characters first.
     if (prec >= 0) {
@@ -779,7 +779,7 @@
         nchars++;
         insize += nconv;
       }
-      if (nconv == (size_t)-1 || nconv == (size_t)-2) return (NULL);
+      if (nconv == (size_t)-1 || nconv == (size_t)-2) return (nullptr);
     } else {
       insize = strlen(mbsarg);
     }
@@ -788,7 +788,7 @@
     // converting at most `size' bytes of the input multibyte string to
     // wide characters for printing.
     wchar_t* convbuf = static_cast<wchar_t*>(calloc(insize + 1, sizeof(*convbuf)));
-    if (convbuf == NULL) return NULL;
+    if (convbuf == nullptr) return nullptr;
     wchar_t* wcp = convbuf;
     p = mbsarg;
     bzero(&mbs, sizeof(mbs));
@@ -802,7 +802,7 @@
     }
     if (nconv == (size_t)-1 || nconv == (size_t)-2) {
       free(convbuf);
-      return NULL;
+      return nullptr;
     }
     *wcp = '\0';
 
diff --git a/libc/stdio/stdio_ext.cpp b/libc/stdio/stdio_ext.cpp
index e17b62a..945813e 100644
--- a/libc/stdio/stdio_ext.cpp
+++ b/libc/stdio/stdio_ext.cpp
@@ -69,7 +69,7 @@
 
 void _flushlbf() {
   // If we flush all streams, we know we've flushed all the line-buffered streams.
-  fflush(NULL);
+  fflush(nullptr);
 }
 
 void __fseterr(FILE* fp) {
diff --git a/libc/stdio/vfprintf.cpp b/libc/stdio/vfprintf.cpp
index 17e4372..7a67868 100644
--- a/libc/stdio/vfprintf.cpp
+++ b/libc/stdio/vfprintf.cpp
@@ -64,7 +64,7 @@
    * D:	expchar holds this character; '\0' if no exponent, e.g. %f
    * F:	at least two digits for decimal, at least one digit for hex
    */
-  char* decimal_point = NULL;
+  char* decimal_point = nullptr;
   int signflag; /* true if float is negative */
   union {       /* floating point arguments %[aAeEfFgG] */
     double dbl;
@@ -77,7 +77,7 @@
   int lead;                   /* sig figs before decimal or group sep */
   int ndig;                   /* actual number of digits returned by dtoa */
   CHAR_TYPE expstr[MAXEXPDIG + 2]; /* buffer for exponent string: e+ZZZ */
-  char* dtoaresult = NULL;
+  char* dtoaresult = nullptr;
 
   uintmax_t _umax;             /* integer arguments %[diouxX] */
   enum { OCT, DEC, HEX } base; /* base for %[diouxX] conversion */
@@ -146,14 +146,14 @@
   }
 
   CHAR_TYPE* fmt = const_cast<CHAR_TYPE*>(fmt0);
-  argtable = NULL;
+  argtable = nullptr;
   nextarg = 1;
   va_copy(orgap, ap);
   uio.uio_iov = iovp = iov;
   uio.uio_resid = 0;
   uio.uio_iovcnt = 0;
   ret = 0;
-  convbuf = NULL;
+  convbuf = nullptr;
 
   /*
    * Scan the format for conversions (`%' character).
@@ -226,7 +226,7 @@
         }
         if (ch == '$') {
           nextarg = n;
-          if (argtable == NULL) {
+          if (argtable == nullptr) {
             argtable = statargtable;
             if (__find_arguments(fmt0, orgap, &argtable, &argtablesiz) == -1) {
               ret = -1;
@@ -261,7 +261,7 @@
         } while (is_digit(ch));
         if (ch == '$') {
           nextarg = n;
-          if (argtable == NULL) {
+          if (argtable == nullptr) {
             argtable = statargtable;
             if (__find_arguments(fmt0, orgap, &argtable, &argtablesiz) == -1) {
               ret = -1;
@@ -353,14 +353,14 @@
         if (flags & LONGDBL) {
           fparg.ldbl = GETARG(long double);
           dtoaresult = cp = __hldtoa(fparg.ldbl, xdigs, prec, &expt, &signflag, &dtoaend);
-          if (dtoaresult == NULL) {
+          if (dtoaresult == nullptr) {
             errno = ENOMEM;
             goto error;
           }
         } else {
           fparg.dbl = GETARG(double);
           dtoaresult = cp = __hdtoa(fparg.dbl, xdigs, prec, &expt, &signflag, &dtoaend);
-          if (dtoaresult == NULL) {
+          if (dtoaresult == nullptr) {
             errno = ENOMEM;
             goto error;
           }
@@ -390,14 +390,14 @@
         if (flags & LONGDBL) {
           fparg.ldbl = GETARG(long double);
           dtoaresult = cp = __ldtoa(&fparg.ldbl, expchar ? 2 : 3, prec, &expt, &signflag, &dtoaend);
-          if (dtoaresult == NULL) {
+          if (dtoaresult == nullptr) {
             errno = ENOMEM;
             goto error;
           }
         } else {
           fparg.dbl = GETARG(double);
           dtoaresult = cp = __dtoa(fparg.dbl, expchar ? 2 : 3, prec, &expt, &signflag, &dtoaend);
-          if (dtoaresult == NULL) {
+          if (dtoaresult == nullptr) {
             errno = ENOMEM;
             goto error;
           }
@@ -479,18 +479,18 @@
           wchar_t* wcp;
 
           free(convbuf);
-          convbuf = NULL;
-          if ((wcp = GETARG(wchar_t*)) == NULL) {
+          convbuf = nullptr;
+          if ((wcp = GETARG(wchar_t*)) == nullptr) {
             cp = const_cast<char*>("(null)");
           } else {
             convbuf = helpers::wcsconv(wcp, prec);
-            if (convbuf == NULL) {
+            if (convbuf == nullptr) {
               ret = -1;
               goto error;
             }
             cp = convbuf;
           }
-        } else if ((cp = GETARG(char*)) == NULL) {
+        } else if ((cp = GETARG(char*)) == nullptr) {
           cp = const_cast<char*>("(null)");
         }
         if (prec >= 0) {
@@ -625,7 +625,7 @@
     if ((flags & FPT) == 0) {
       PRINT(cp, size);
     } else { /* glue together f_p fragments */
-      if (decimal_point == NULL) decimal_point = nl_langinfo(RADIXCHAR);
+      if (decimal_point == nullptr) decimal_point = nl_langinfo(RADIXCHAR);
       if (!expchar) { /* %[fF] or sufficiently short %[gG] */
         if (expt <= 0) {
           PRINT(zeroes, 1);
@@ -676,9 +676,9 @@
 finish:
   free(convbuf);
   if (dtoaresult) __freedtoa(dtoaresult);
-  if (argtable != NULL && argtable != statargtable) {
+  if (argtable != nullptr && argtable != statargtable) {
     munmap(argtable, argtablesiz);
-    argtable = NULL;
+    argtable = nullptr;
   }
   return (ret);
 }
diff --git a/libc/stdio/vfscanf.cpp b/libc/stdio/vfscanf.cpp
index 49d6bf6..0fcdbed 100644
--- a/libc/stdio/vfscanf.cpp
+++ b/libc/stdio/vfscanf.cpp
@@ -97,7 +97,7 @@
   char buf[BUF];    /* buffer for numeric conversions */
   size_t nconv;     /* length of multibyte sequence converted */
   mbstate_t mbs;
-  void* allocation = NULL; // Allocated but unassigned result for %mc/%ms/%m[.
+  void* allocation = nullptr; // Allocated but unassigned result for %mc/%ms/%m[.
   size_t capacity = 0; // Number of char/wchar_t units allocated in `allocation`.
 
   /* `basefix' is used to avoid `if' tests in the integer scanner */
@@ -334,9 +334,9 @@
         if (flags & LONG) {
           if (flags & ALLOCATE) {
             allocation = wcp = reinterpret_cast<wchar_t*>(malloc(width * sizeof(wchar_t)));
-            if (allocation == NULL) goto allocation_failure;
+            if (allocation == nullptr) goto allocation_failure;
           } else if (flags & SUPPRESS) {
-            wcp = NULL;
+            wcp = nullptr;
           } else {
             wcp = va_arg(ap, wchar_t*);
           }
@@ -370,9 +370,9 @@
               break;
             }
           }
-          if (allocation != NULL) {
+          if (allocation != nullptr) {
             *va_arg(ap, wchar_t**) = reinterpret_cast<wchar_t*>(allocation);
-            allocation = NULL;
+            allocation = nullptr;
           }
           if (!(flags & SUPPRESS)) nassigned++;
         } else if (flags & SUPPRESS) {
@@ -397,15 +397,15 @@
         } else {
           if (flags & ALLOCATE) {
             allocation = p = reinterpret_cast<char*>(malloc(width));
-            if (allocation == NULL) goto allocation_failure;
+            if (allocation == nullptr) goto allocation_failure;
           } else {
             p = va_arg(ap, char*);
           }
           size_t r = fread(p, 1, width, fp);
           if (r == 0) goto input_failure;
-          if (allocation != NULL) {
+          if (allocation != nullptr) {
             *va_arg(ap, char**) = reinterpret_cast<char*>(allocation);
-            allocation = NULL;
+            allocation = nullptr;
           }
           nread += r;
           nassigned++;
@@ -423,9 +423,9 @@
           if (flags & ALLOCATE) {
             capacity = MIN(width, 32);
             allocation = wcp = reinterpret_cast<wchar_t*>(malloc(sizeof(wchar_t) * capacity));
-            if (allocation == NULL) goto allocation_failure;
+            if (allocation == nullptr) goto allocation_failure;
           } else if (flags & SUPPRESS) {
-            wcp = NULL;
+            wcp = nullptr;
           } else {
             wcp = va_arg(ap, wchar_t*);
           }
@@ -455,11 +455,11 @@
               }
               if (wcp) wcp[n] = wc;
               n++;
-              if (allocation != NULL && n == capacity) {
+              if (allocation != nullptr && n == capacity) {
                 capacity *= 2;
                 wchar_t* new_allocation =
                     reinterpret_cast<wchar_t*>(realloc(allocation, sizeof(wchar_t) * capacity));
-                if (new_allocation == NULL) goto allocation_failure;
+                if (new_allocation == nullptr) goto allocation_failure;
                 allocation = wcp = new_allocation;
               }
               nread += bytes;
@@ -478,9 +478,9 @@
             fp->_flags |= __SERR;
             goto input_failure;
           }
-          if (allocation != NULL) {
+          if (allocation != nullptr) {
             *va_arg(ap, wchar_t**) = reinterpret_cast<wchar_t*>(allocation);
-            allocation = NULL;
+            allocation = nullptr;
           }
         } else if (flags & SUPPRESS) {
           n = 0;
@@ -497,7 +497,7 @@
           if (flags & ALLOCATE) {
             capacity = MIN(width, 32);
             allocation = p = reinterpret_cast<char*>(malloc(capacity));
-            if (allocation == NULL) goto allocation_failure;
+            if (allocation == nullptr) goto allocation_failure;
           } else {
             p = va_arg(ap, char*);
           }
@@ -505,10 +505,10 @@
           while (ccltab[*fp->_p]) {
             fp->_r--;
             p[n++] = *fp->_p++;
-            if (allocation != NULL && n == capacity) {
+            if (allocation != nullptr && n == capacity) {
               capacity *= 2;
               char* new_allocation = reinterpret_cast<char*>(realloc(allocation, capacity));
-              if (new_allocation == NULL) goto allocation_failure;
+              if (new_allocation == nullptr) goto allocation_failure;
               allocation = p = new_allocation;
             }
             if (--width == 0) break;
@@ -518,9 +518,9 @@
             }
           }
           nread += n;
-          if (allocation != NULL) {
+          if (allocation != nullptr) {
             *va_arg(ap, char**) = reinterpret_cast<char*>(allocation);
-            allocation = NULL;
+            allocation = nullptr;
           }
         }
         if (c == CT_CCL && n == 0) goto match_failure;
@@ -671,9 +671,9 @@
 
           *p = '\0';
           if (flags & UNSIGNED) {
-            res = strtoumax(buf, NULL, base);
+            res = strtoumax(buf, nullptr, base);
           } else {
-            res = strtoimax(buf, NULL, base);
+            res = strtoimax(buf, nullptr, base);
           }
           if (flags & POINTER) {
             *va_arg(ap, void**) = (void*)(uintptr_t)res;
diff --git a/libc/stdio/vfwprintf.cpp b/libc/stdio/vfwprintf.cpp
index 46b6233..ae0b62f 100644
--- a/libc/stdio/vfwprintf.cpp
+++ b/libc/stdio/vfwprintf.cpp
@@ -64,7 +64,7 @@
    * D:	expchar holds this character; '\0' if no exponent, e.g. %f
    * F:	at least two digits for decimal, at least one digit for hex
    */
-  char* decimal_point = NULL;
+  char* decimal_point = nullptr;
   int signflag; /* true if float is negative */
   union {       /* floating point arguments %[aAeEfFgG] */
     double dbl;
@@ -77,7 +77,7 @@
   int lead;                      /* sig figs before decimal or group sep */
   int ndig;                      /* actual number of digits returned by dtoa */
   CHAR_TYPE expstr[MAXEXPDIG + 2]; /* buffer for exponent string: e+ZZZ */
-  char* dtoaresult = NULL;
+  char* dtoaresult = nullptr;
 
   uintmax_t _umax;             /* integer arguments %[diouxX] */
   enum { OCT, DEC, HEX } base; /* base for %[diouxX] conversion */
@@ -135,14 +135,14 @@
   }
 
   CHAR_TYPE* fmt = const_cast<CHAR_TYPE*>(fmt0);
-  argtable = NULL;
+  argtable = nullptr;
   nextarg = 1;
   va_copy(orgap, ap);
   uio.uio_iov = iovp = iov;
   uio.uio_resid = 0;
   uio.uio_iovcnt = 0;
   ret = 0;
-  convbuf = NULL;
+  convbuf = nullptr;
 
   /*
    * Scan the format for conversions (`%' character).
@@ -215,7 +215,7 @@
         }
         if (ch == '$') {
           nextarg = n;
-          if (argtable == NULL) {
+          if (argtable == nullptr) {
             argtable = statargtable;
             if (__find_arguments(fmt0, orgap, &argtable, &argtablesiz) == -1) {
               ret = -1;
@@ -250,7 +250,7 @@
         } while (is_digit(ch));
         if (ch == '$') {
           nextarg = n;
-          if (argtable == NULL) {
+          if (argtable == nullptr) {
             argtable = statargtable;
             if (__find_arguments(fmt0, orgap, &argtable, &argtablesiz) == -1) {
               ret = -1;
@@ -331,14 +331,14 @@
         if (flags & LONGDBL) {
           fparg.ldbl = GETARG(long double);
           dtoaresult = __hldtoa(fparg.ldbl, xdigs, prec, &expt, &signflag, &dtoaend);
-          if (dtoaresult == NULL) {
+          if (dtoaresult == nullptr) {
             errno = ENOMEM;
             goto error;
           }
         } else {
           fparg.dbl = GETARG(double);
           dtoaresult = __hdtoa(fparg.dbl, xdigs, prec, &expt, &signflag, &dtoaend);
-          if (dtoaresult == NULL) {
+          if (dtoaresult == nullptr) {
             errno = ENOMEM;
             goto error;
           }
@@ -347,7 +347,7 @@
         if (expt == INT_MAX) ox[1] = '\0';
         free(convbuf);
         cp = convbuf = helpers::mbsconv(dtoaresult, -1);
-        if (cp == NULL) goto error;
+        if (cp == nullptr) goto error;
         ndig = dtoaend - dtoaresult;
         goto fp_common;
       case 'e':
@@ -372,14 +372,14 @@
         if (flags & LONGDBL) {
           fparg.ldbl = GETARG(long double);
           dtoaresult = __ldtoa(&fparg.ldbl, expchar ? 2 : 3, prec, &expt, &signflag, &dtoaend);
-          if (dtoaresult == NULL) {
+          if (dtoaresult == nullptr) {
             errno = ENOMEM;
             goto error;
           }
         } else {
           fparg.dbl = GETARG(double);
           dtoaresult = __dtoa(fparg.dbl, expchar ? 2 : 3, prec, &expt, &signflag, &dtoaend);
-          if (dtoaresult == NULL) {
+          if (dtoaresult == nullptr) {
             errno = ENOMEM;
             goto error;
           }
@@ -387,7 +387,7 @@
         }
         free(convbuf);
         cp = convbuf = helpers::mbsconv(dtoaresult, -1);
-        if (cp == NULL) goto error;
+        if (cp == nullptr) goto error;
         ndig = dtoaend - dtoaresult;
       fp_common:
         if (signflag) sign = '-';
@@ -461,13 +461,13 @@
         /*FALLTHROUGH*/
       case 's':
         if (flags & LONGINT) {
-          if ((cp = GETARG(wchar_t*)) == NULL) cp = const_cast<wchar_t*>(L"(null)");
+          if ((cp = GETARG(wchar_t*)) == nullptr) cp = const_cast<wchar_t*>(L"(null)");
         } else {
           char* mbsarg;
-          if ((mbsarg = GETARG(char*)) == NULL) mbsarg = const_cast<char*>("(null)");
+          if ((mbsarg = GETARG(char*)) == nullptr) mbsarg = const_cast<char*>("(null)");
           free(convbuf);
           convbuf = helpers::mbsconv(mbsarg, prec);
-          if (convbuf == NULL) {
+          if (convbuf == nullptr) {
             fp->_flags |= __SERR;
             goto error;
           } else {
@@ -606,7 +606,7 @@
     if ((flags & FPT) == 0) {
       PRINT(cp, size);
     } else { /* glue together f_p fragments */
-      if (decimal_point == NULL) decimal_point = nl_langinfo(RADIXCHAR);
+      if (decimal_point == nullptr) decimal_point = nl_langinfo(RADIXCHAR);
       if (!expchar) { /* %[fF] or sufficiently short %[gG] */
         if (expt <= 0) {
           PRINT(zeroes, 1);
@@ -654,9 +654,9 @@
 finish:
   free(convbuf);
   if (dtoaresult) __freedtoa(dtoaresult);
-  if (argtable != NULL && argtable != statargtable) {
+  if (argtable != nullptr && argtable != statargtable) {
     munmap(argtable, argtablesiz);
-    argtable = NULL;
+    argtable = nullptr;
   }
   return (ret);
 }