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Commit 08929cc3 authored by Elliott Hughes's avatar Elliott Hughes
Browse files

Avoid zero-initializing our most-used buffers. 

The StringPrintf one is heavily used and brings the overhead versus
fmtlib down to 1.5x rather than 2x. I don't have a convenient benchmark
for the other two.

Test: libbase tests & benchmarks
Bug: http://b/155324241
Change-Id: I9e704a360846d5520c53f668e7c315b0c0ea55f8
(cherry picked from commit 8c253d4d)
parent 053ade43

base/file.cpp

+1 −1
Original line number Diff line number Diff line
@@ -225,7 +225,7 @@ bool ReadFdToString(borrowed_fd fd, std::string* content) { 
    content->reserve(sb.st_size);

  }



  char buf[BUFSIZ];

  char buf[BUFSIZ] __attribute__((__uninitialized__));

  ssize_t n;

  while ((n = TEMP_FAILURE_RETRY(read(fd.get(), &buf[0], sizeof(buf)))) > 0) {

    content->append(buf, n);

base/logging.cpp

+1 −1
Original line number Diff line number Diff line
@@ -260,7 +260,7 @@ static void KernelLogLine(const char* msg, int length, android::base::LogSeverit 
  // The kernel's printk buffer is only 1024 bytes.

  // TODO: should we automatically break up long lines into multiple lines?

  // Or we could log but with something like "..." at the end?

  char buf[1024];

  char buf[1024] __attribute__((__uninitialized__));

  size_t size = snprintf(buf, sizeof(buf), "<%d>%s: %.*s\n", level, tag, length, msg);

  if (size > sizeof(buf)) {

    size = snprintf(buf, sizeof(buf), "<%d>%s: %zu-byte message too long for printk\n",

base/stringprintf.cpp

+1 −1
Original line number Diff line number Diff line
@@ -25,7 +25,7 @@ namespace base { 


void StringAppendV(std::string* dst, const char* format, va_list ap) {

  // First try with a small fixed size buffer

  char space[1024];

  char space[1024] __attribute__((__uninitialized__));



  // It's possible for methods that use a va_list to invalidate

  // the data in it upon use.  The fix is to make a copy