Disable pedantic checks by default

They can be re-enabled via `PEDANTIC_CHECKS`

Author: jvoisin

README.md

@@ -28,8 +28,10 @@ on Clang. It was initially intended to be used on
   [significant coverage](https://jvoisin.github.io/fortify-headers/)
 - Defining `USE_NATIVE_CHK` will make use of compiler-provided builtin `_chk`
   functions, which might be a bit better in term of diagnostics,
-  but won't necesarily provide the same amount of security checks.
-
+  but won't necessarily provide the same amount of security checks.
+- Defining `PEDANTIC_CHECKS` will enable pedantic checks, that while technically
+  correct, might break some programs relying on widely accepted
+  undefined-behaviours.
 
 # Sample usage
 

include/string.h

@@ -51,8 +51,10 @@ __error_if((__fh_bos(__od, 0) < __n), "'memcpy' called with `n` bigger than the
 #if __has_builtin(__builtin___memcpy_chk) && USE_NATIVE_CHK
 	return __builtin___memcpy_chk(__od, __os, __n, __fh_bos(__od, 0));
 #else
+#if defined PEDANTIC_CHECKS
 	if (!__od || !__os)
       		__builtin_trap();
+#endif
 
 	__fh_size_t __bd = __fh_bos(__od, 0);
 	__fh_size_t __bs = __fh_bos(__os, 0);
@@ -78,8 +80,10 @@ _FORTIFY_FN(memmove) void *memmove(void * _FORTIFY_POS0 __d,
 #if __has_builtin(__builtin___memmove_chk) && USE_NATIVE_CHK
 	return __builtin___memmove_chk(__d, __s, __n, __fh_bos(__d, 0));
 #else
+#if defined PEDANTIC_CHECKS
 	if (!__d || !__s)
 		__builtin_trap();
+#endif
 
 	__fh_size_t __bd = __fh_bos(__d, 0);
 	__fh_size_t __bs = __fh_bos(__s, 0);
@@ -100,8 +104,10 @@ __warning_if(__c != 0 && __n == 0, "'memset' will set `0` bytes; did you invert
 #if __has_builtin(__builtin___memset_chk) && USE_NATIVE_CHK
 	return __builtin___memset_chk(__d, __c, __n, __fh_bos(__d, 0));
 #else
+#if defined PEDANTIC_CHECKS
 	if (!__d)
 		__builtin_trap();
+#endif
 
 	__fh_size_t __b = __fh_bos(__d, 0);
 
@@ -120,13 +126,14 @@ _FORTIFY_FN(memchr) void *memchr(const void * _FORTIFY_POS0 __d, int __c, size_t
 #if __has_builtin(__builtin___memchr_chk) && USE_NATIVE_CHK
 	return __builtin___memchr_chk(__d, __c, __n, __fh_bos(__d, 0));
 #else
+#if defined PEDANTIC_CHECKS
 	if (!__d)
 		__builtin_trap();
-
 #if __STDC_VERSION__ < 201112L
 	__fh_size_t __b = __fh_bos(__d, 0);
 	if (__n > __b)
 		__builtin_trap();
+#endif
 #endif
 
 	return __builtin_memchr(__d, __c, __n);

tests/Makefile

@@ -1,4 +1,4 @@
-CFLAGS+=-I../include/ -D_FORTIFY_SOURCE=3 -static -O2
+CFLAGS+=-I../include/ -D_FORTIFY_SOURCE=3 -static -O2 -DPEDANTIC_CHECKS
 
 COMPTIME_TARGETS= \
 	test_memcpy_overwrite_under  \