3 files changed, 13 insertions, 4 deletions

diff --git a/README.md b/README.md
index 21d3ccf..9b9a956 100644
--- a/README.md
+++ b/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
 
diff --git a/include/string.h b/include/string.h
index db2e6c3..071d592 100644
--- a/include/string.h
+++ b/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);
 
@@ -120,14 +126,15 @@ _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);
 #endif
diff --git a/tests/Makefile b/tests/Makefile
index b1223ea..8faf11a 100644
--- a/tests/Makefile
+++ b/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  \