Upstreaming diffs in os_compat_android.cc

base/os_compat_android.cc

Index: base/os_compat_android.cc
diff --git a/base/os_compat_android.cc b/base/os_compat_android.cc
index e8b6e2fa941a21324b709dc24955cd9b4fbacdd2..af079eafe2cfb1505ea3d2a4b9564008ea30a1a4 100644
--- a/base/os_compat_android.cc
+++ b/base/os_compat_android.cc
@@ -4,8 +4,13 @@
 
 #include "base/os_compat_android.h"
 
+#include <errno.h>
+#include <math.h>
+#include <sys/stat.h>
 #include <time64.h>
 
+#include "base/rand_util.h"
+#include "base/string_piece.h"
 #include "base/stringprintf.h"
 
 // There is no futimes() avaiable in Bionic, so we provide our own
@@ -29,4 +34,122 @@ time_t timegm(struct tm* const t) {
   return result;
 }
 
+// The following is only needed when building with GCC 4.6 or higher
+// (i.e. not with Android GCC 4.4.3, nor with Clang).
+//
+// GCC is now capable of optimizing successive calls to sin() and cos() into
+// a single call to sincos(). This means that source code that looks like:
+//
+//     double c, s;
+//     c = cos(angle);
+//     s = sin(angle);
+//
+// Will generate machine code that looks like:
+//
+//     double c, s;
+//     sincos(angle, &s, &c);
+//
+// Unfortunately, sincos() and friends are not part of the Android libm.so
+// library provided by the NDK for API level 9. When the optimization kicks
+// in, it makes the final build fail with a puzzling message (puzzling
+// because 'sincos' doesn't appear anywhere in the sources!).
+//
+// To solve this, we provide our own implementation of the sincos() function
+// and related friends. Note that we must also explicitely tell GCC to disable
+// optimizations when generating these. Otherwise, the generated machine code
+// for each function would simply end up calling itself, resulting in a
+// runtime crash due to stack overflow.
+//
+#if defined(__GNUC__) && !defined(__clang__)
+
+// For the record, Clang does not support the 'optimize' attribute.
+// In the unlikely event that it begins performing this optimization too,
+// we'll have to find a different way to achieve this. NOTE: Tested with O1
+// which still performs the optimization.
+//
+#define GCC_NO_OPTIMIZE  __attribute__((optimize("O0")))
+
+GCC_NO_OPTIMIZE
+void sincos(double angle, double* s, double *c) {
+  *c = cos(angle);
+  *s = sin(angle);
+}
+
+GCC_NO_OPTIMIZE
+void sincosf(float angle, float* s, float* c) {
+  *c = cosf(angle);
+  *s = sinf(angle);
+}
+
+#endif // __GNUC__ && !__clang__
+
+// An implementation of mkdtemp, since it is not exposed by the NDK
+// for native API level 9 that we target.
+//
+// For any changes in the mkdtemp function, you should manually run the unittest
+// OsCompatAndroidTest.DISABLED_TestMkdTemp in your local machine to check if it
+// passes. Please don't enable it, since it creates a directory and may be
+// source of flakyness.
+char* mkdtemp(char* path) {
+  if (path == NULL) {
+    errno = EINVAL;
+    return NULL;
+  }
+
+  const int path_len = strlen(path);
+
+  // The last six characters of 'path' must be XXXXXX.
+  const base::StringPiece kSuffix("XXXXXX");
+  const int kSuffixLen = kSuffix.length();
+  if (!base::StringPiece(path, path_len).ends_with(kSuffix)) {
+    errno = EINVAL;
+    return NULL;
+  }
+
+  // If the path contains a directory, as in /tmp/foo/XXXXXXXX, make sure
+  // that /tmp/foo exists, otherwise we're going to loop a really long
+  // time for nothing below
+  char* dirsep = strrchr(path, '/');
+  if (dirsep != NULL) {
+    struct stat st;
+    int ret;
+
+    *dirsep = '\0';  // Terminating directory path temporarily
+
+    ret = stat(path, &st);
+
+    *dirsep = '/';  // Restoring directory separator
+    if (ret < 0)  // Directory probably does not exist
+      return NULL;
+    if (!S_ISDIR(st.st_mode)) {  // Not a directory
+      errno = ENOTDIR;
+      return NULL;
+    }
+  }
+
+  // Max number of tries using different random suffixes.
+  const int kMaxTries = 100;
+
+  // Now loop until we CAN create a directory by that name or we reach the max
+  // number of tries.
+  for (int i = 0; i < kMaxTries; ++i) {
+    // Fill the suffix XXXXXX with a random string composed of a-z chars.
+    for (int pos = 0; pos < kSuffixLen; ++pos) {
+      char rand_char = static_cast<char>(base::RandInt('a', 'z'));
+      path[path_len - kSuffixLen + pos] = rand_char;
+    }
+    if (mkdir(path, 0700) == 0) {
+      // We just created the directory succesfully.
+      return path;
+    }
+    if (errno != EEXIST) {
+      // The directory doesn't exist, but an error occured
+      return NULL;
+    }
+  }
+
+  // We reached the max number of tries.
+  return NULL;
+}
+
 }  // extern "C"