commit 027614c263b4a1ae6f74e3470723f97331af8baa Author: Taylor Yu catalyst@torproject.org Date: Fri May 26 17:04:52 2017 -0400

Ensure that uint8_t is unsigned char

Many places in our code assume that uint8_t is the same type as unsigned char. Test this assumption in the configure script. This is important because of the privileged aliasing properties of character types in C.

Fixes #22410. --- changes/bug22410 | 4 ++++ configure.ac | 18 ++++++++++++++++++ 2 files changed, 22 insertions(+)

diff --git a/changes/bug22410 b/changes/bug22410 new file mode 100644 index 0000000..678a26d --- /dev/null +++ b/changes/bug22410 @@ -0,0 +1,4 @@ + o Minor bugfixes (portability): + - Check at configure time whether uint8_t is unsigned char. Lots + of existing code already assumes this, and there could be strict + aliasing issues if they aren't the same type. Fixes #22410. diff --git a/configure.ac b/configure.ac index 0c673d0..e8b35e8 100644 --- a/configure.ac +++ b/configure.ac @@ -1552,6 +1552,24 @@ if test "$tor_cv_sign_extend" != "no"; then [Define to 1 iff right-shifting a negative value performs sign-extension]) fi

+# Is uint8_t the same type as unsigned char? +AC_CACHE_CHECK([whether uint8_t is the same type as unsigned char], tor_cv_uint8_uchar, +[AC_COMPILE_IFELSE([AC_LANG_SOURCE([[ +#include <stdint.h> +extern uint8_t c; +unsigned char c;]])], + [tor_cv_uint8_uchar=yes], + [tor_cv_uint8_uchar=no], + [tor_cv_uint8_uchar=cross])]) + +if test "$tor_cv_uint8_uchar" = "cross"; then + AC_MSG_NOTICE([Cross-compiling: we'll assume that uint8_t is the same type as unsigned char]) +fi + +if test "$tor_cv_uint8_uchar" = "no"; then + AC_MSG_ERROR([We assume that uint8_t is the same type as unsigned char, but your compiler disagrees.]) +fi + # Whether we should use the dmalloc memory allocation debugging library. AC_MSG_CHECKING(whether to use dmalloc (debug memory allocation library)) AC_ARG_WITH(dmalloc,