NUL byte is never sent to user callback (#133)

* NUL byte is never sent to user callback * cstring for memset
charlesnicholson · Jan 19, 2022 · 8b801d4 · 8b801d4
1 parent d89963a
commit 8b801d4
Show file tree

Hide file tree

Showing 3 changed files with 25 additions and 13 deletions.
diff --git a/nanoprintf.h b/nanoprintf.h
@@ -1117,8 +1117,7 @@ int npf_vpprintf(npf_putc pc, void *pc_ctx, char const *format, va_list vlist) {
     cur += fs_len;
   }
 
-  NPF_PUTC('\0');
-  return n - 1;
+  return n;
 }
 
 #undef NPF_PUTC
@@ -1146,10 +1145,11 @@ int npf_vsnprintf(char *buffer, size_t bufsz, char const *format, va_list vlist)
   bufputc_ctx.dst = buffer;
   bufputc_ctx.len = bufsz;
   bufputc_ctx.cur = 0;
-  if (buffer && bufsz) { buffer[bufsz - 1] = 0; }
 
-  return
-    npf_vpprintf(buffer ? npf_bufputc : npf_bufputc_nop, &bufputc_ctx, format, vlist);
+  npf_putc const pc = buffer ? npf_bufputc : npf_bufputc_nop;
+  int const n = npf_vpprintf(pc, &bufputc_ctx, format, vlist);
+  pc('\0', &bufputc_ctx);
+  return n;
 }
 
 #endif // NANOPRINTF_IMPLEMENTATION_INCLUDED

diff --git a/tests/unit_snprintf.cc b/tests/unit_snprintf.cc
@@ -1,12 +1,26 @@
 #include "unit_nanoprintf.h"
 #include "doctest.h"
 
+#include <cstring>
 #include <string>
 #include <iostream>
 
 TEST_CASE("npf_snprintf") {
   char buf[128];
 
+  SUBCASE("empty string has null terminator") {
+    memset(buf, 0xFF, sizeof(buf));
+    npf_snprintf(buf, sizeof(buf), "");
+    REQUIRE(buf[0] == '\0');
+  }
+
+  SUBCASE("string has null terminator") {
+    memset(buf, 0xFF, sizeof(buf));
+    npf_snprintf(buf, sizeof(buf), "Hello");
+    REQUIRE(buf[5] == '\0');
+    REQUIRE(std::string{buf} == "Hello");
+  }
+
   SUBCASE("returns number of printed characters without null terminator") {
     REQUIRE(!npf_snprintf(buf, sizeof(buf), ""));
     REQUIRE(npf_snprintf(buf, sizeof(buf), "a") == 1);

diff --git a/tests/unit_vpprintf.cc b/tests/unit_vpprintf.cc
@@ -13,7 +13,7 @@ struct Recorder {
   }
 
   std::string String() const {
-    return calls.empty() ? std::string() : std::string(calls.begin(), calls.end() - 1);
+    return calls.empty() ? std::string() : std::string(calls.begin(), calls.end());
   }
 
   std::vector<int> calls;
@@ -22,20 +22,18 @@ struct Recorder {
 TEST_CASE("npf_vpprintf") {
   Recorder r;
 
-  SUBCASE("empty string only holds null terminator") {
+  SUBCASE("empty string never calls callback") {
     REQUIRE(npf_pprintf(r.PutC, &r, "") == 0);
-    REQUIRE(r.calls.size() == 1);
-    REQUIRE(r.calls[0] == '\0');
+    REQUIRE(r.calls.empty());
   }
 
-  SUBCASE("single character then null terminator") {
+  SUBCASE("single character string") {
     REQUIRE(npf_pprintf(r.PutC, &r, "A") == 1);
-    REQUIRE(r.calls.size() == 2);
+    REQUIRE(r.calls.size() == 1);
     REQUIRE(r.calls[0] == 'A');
-    REQUIRE(r.calls[1] == '\0');
   }
 
-  SUBCASE("string without format specifiers then null terminator") {
+  SUBCASE("string without format specifiers") {
     std::string const s{"Hello from nanoprintf!"};
     REQUIRE(npf_pprintf(r.PutC, &r, s.c_str()) == (int)s.size());
     REQUIRE(s == r.String());