Fix perfetto build with gcc 5.3

The libstdc++ header <cmath> undefines the signbit macro of the libc header
<math.h>. Perfetto's header "string_writer.h" uses the signbit macro.

In GCC 5.3, we have the include chain

  <regex> -> <bits/stl_algo.h> -> <random> -> <cmath>,

meaning <regex> cannot be used together with the signbit macro. But this is
exactly what Perfetto's "systrace_trace_parser.cc" does: it transitively
includes <regex> and "string_writer.h"; it thus fails to build with GCC 5.3.

In GCC 5.4 and 6, the include chain is changed to

  <regex> -> <bits/stl_algo.h> -> <bits/uniform_int_dist.h>,

and the build the succeeds.

Fix by using <cmath> and std::signbit in "string_writer.h".

Change-Id: Id67001f90c7d91cf97dc4c46654905bcb92fb066
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>

1 files changed, 2 insertions, 2 deletions

diff --git a/chromium/third_party/perfetto/include/perfetto/ext/base/string_writer.h b/chromium/third_party/perfetto/include/perfetto/ext/base/string_writer.h
index 681324f18eb..bd5d301bf4e 100644
--- a/chromium/third_party/perfetto/include/perfetto/ext/base/string_writer.h
+++ b/chromium/third_party/perfetto/include/perfetto/ext/base/string_writer.h
@@ -18,7 +18,7 @@
 #define INCLUDE_PERFETTO_EXT_BASE_STRING_WRITER_H_
 
 #include <inttypes.h>
-#include <math.h>
+#include <cmath>
 #include <stdlib.h>
 #include <string.h>
 #include <limits>
@@ -69,7 +69,7 @@ class StringWriter {
   // digits of the integer is less than |padding|.
   template <char padchar, uint64_t padding>
   void AppendPaddedInt(int64_t sign_value) {
-    const bool negate = signbit(static_cast<double>(sign_value));
+    const bool negate = std::signbit(static_cast<double>(sign_value));
     uint64_t absolute_value = static_cast<uint64_t>(std::abs(sign_value));
     AppendPaddedInt<padchar, padding>(absolute_value, negate);
   }