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src: don't include a null character in the WriteConsoleW call #7764

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src: don't include a null character in the WriteConsoleW call #7764

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5dc5e74
src: don't include a null character in the WriteConsoleW call
seishun Jul 16, 2016
d325fbe
different approach
seishun Jul 17, 2016
8e246c5
add a check
seishun Aug 21, 2016
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src: don't include a null character in the WriteConsoleW call 
Fixes: #7755
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@seishun
seishun committed Aug 21, 2016
commit 5dc5e74a6fa8bc15dc67bfe878e9efe20073229e
2 changes: 1 addition & 1 deletion src/node.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -253,7 +253,7 @@ static void PrintErrorString(const char* format, ...) {
vsprintf(out.data(), format, ap);

// Get required wide buffer size
n = MultiByteToWideChar(CP_UTF8, 0, out.data(), -1, nullptr, 0);
n = MultiByteToWideChar(CP_UTF8, 0, out.data(), n, nullptr, 0);
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@bnoordhuis bnoordhuis Jul 17, 2016

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I don't think this works, it's going to fail when n == 0. (Also, passing n here but -1 three lines below doesn't look Obviously Correct to me.)

I think the patch should look something like this, using explicit sizes everywhere.

diff --git a/src/node.cc b/src/node.cc
index 3998659..1f0ba27 100644
--- a/src/node.cc
+++ b/src/node.cc
@@ -246,16 +246,19 @@ static void PrintErrorString(const char* format, ...) {
   }

   // Fill in any placeholders
-  int n = _vscprintf(format, ap);
-  std::vector<char> out(n + 1);
-  vsprintf(out.data(), format, ap);
+  const int numbytes = _vscprintf(format, ap);
+  if (numbytes <= 0) return;
+  std::vector<char> bytes(numbytes + 1);
+  vsprintf(bytes.data(), format, ap);

   // Get required wide buffer size
-  n = MultiByteToWideChar(CP_UTF8, 0, out.data(), -1, nullptr, 0);
-
-  std::vector<wchar_t> wbuf(n);
-  MultiByteToWideChar(CP_UTF8, 0, out.data(), -1, wbuf.data(), n);
-  WriteConsoleW(stderr_handle, wbuf.data(), n, nullptr, nullptr);
+  const int numchars =
+      MultiByteToWideChar(CP_UTF8, 0, bytes.data(), numbytes, nullptr, 0);
+  std::vector<wchar_t> chars(numchars);
+  MultiByteToWideChar(CP_UTF8, 0,
+                      bytes.data(), numbytes,
+                      chars.data(), numchars);
+  WriteConsoleW(stderr_handle, chars.data(), numchars, nullptr, nullptr);
 #else
   vfprintf(stderr, format, ap);
 #endif

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@seishun seishun Jul 17, 2016

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OK, agreed, I'll make it simpler. (I wanted to avoid allocating for the unused wide null character, but it's not worth it if it makes the code more complicated)


std::vector<wchar_t> wbuf(n);
MultiByteToWideChar(CP_UTF8, 0, out.data(), -1, wbuf.data(), n);
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