Calling strlen null pointer

Fix pow qNaN, 0 result with -lieee bug , remove dead parts of wrappers. Fix hypot sNaN handling bug Fix typo in last ChangeLog message.

Fix tests-printers handling for cross compiling. Use Linux 4. Add [BZ ] marker to ChangeLog entry. Fix generic fmax, fmin sNaN handling bug Fix powerpc fmax, fmin sNaN handling bug Document sNaN argument error handling. Add fmaxmag, fminmag functions. Add preprocessor indentation for llogb macro in tgmath. Add roundeven, roundevenf, roundevenl.

Update miscellaneous files from upstream sources. Add fromfp functions. Update config. Correct MIPS math-tests. Fix MIPS n32 lseek, lseek64 bug Update i libm-test-ulps. Fix MIPS n64 readahead bug Increase some test timeouts. Make fallback fesetexceptflag always succeed bug Update MicroBlaze localplt. XFAIL libm-test. Fix ld-address format-truncation error. Fix testsuite build for GCC 7 -Wformat-truncation. Make endian-conversion macros always return correct types bug Make fallback fegetexceptflag work with generic fetestexceptflag.

Make soft-float powerpc swapcontext restore the signal mask bug Update install. Avoid parallel GCC install in build-many-glibcs. Remove very old libm-test-ulps entries. Maciej W. Make common nextdown implementation generic.

Make common fmax implementation generic. Make common fmin implementation generic. S Regenerate ULPs. S Use Clike atomics instead of plain memory accesses in lock elision code. Steve Ellcey 14 : Fix -Wformat-length warning in tst-setgetname. Add atomic operations required by the new condition variable. Use Clike atomics instead of plain memory accesses in x86 lock elision. Robust mutexes: Fix lost wake-up. New condvar implementation that provides stronger ordering guarantees.

New pthread rwlock that is more scalable. Add compiler barriers around modifications of the robust mutex list. Fix mutex pretty printer test and pretty printer output. Instead of calling strpbrk which This patch cleans up the strsep implementation and improves performance. Zack Weinberg 20 : Add utility macros for clang detection, and deprecation with messages. Installed-header hygiene BZ : Simple self-contained fixes. Installed-header hygiene BZ : conditionally defined structures.

Installed-header hygiene BZ : time. Installed header hygiene BZ : Test of installed headers. Minor correction to the "installed header hygiene" patches. Fix build-and-build-again bug in sunrpc tests.

Forgot to add the ChangeLog to the previous commit, doh. Correct comments in string. Tested compilation for aarch64 GCC mainline with build-many-glibcs. This causes errors building glibc tests that deliberately test failure of very large allocations. This patch arranges for this warning to be ignored around the problematic function calls. This patch fixes the glibc testsuite build for GCC 7 -Wformat-truncation, newly moved out of -Wformat-length and with some further warnings that didn't previously appear.

John Bode John Bode k 17 17 gold badges silver badges bronze badges. Stoian Ivanov Stoian Ivanov 77 1 1 silver badge 3 3 bronze badges. Avoid macros in the first place. Three significant reasons: The standard library and the C language are designed assuming that the programmer knows what he is doing, so a null pointer isn't treated as an edge case, but rather as a programmer's mistake that results in undefined behaviour; It incurs runtime overhead - calling strlen thousands of times and always doing str!

Blagovest Buyukliev Blagovest Buyukliev The third reason is also bogus because putting a few extra checks in the library adds less to code size on a typical, non-embedded platform than all the checks inserted in client code.

Show 1 more comment. Casey Flynn Casey Flynn Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. The Overflow Blog. Stack Gives Back Safety in numbers: crowdsourcing data on nefarious IP addresses. Featured on Meta. New post summary designs on greatest hits now, everywhere else eventually. Visit chat. Linked 4. Related Hot Network Questions. To me, it wouldn't strike me as unreasonable for strlen NULL to return 0.

That's reasonable, I was just curious. Ingo Menger. Return WHAT? Perhaps 0, so the caller is led to believe that there is an empty string? Or No wait, this is an unsigned return type, so it couldn't. How about ? Surely, nobody ever has such a long string? C99, 7. Clever Monkey. Good description.

I'll add to this by stating that folks often conflate the null pointer and the null or NUL, if that's how you roll byte at the end of a C-string. I can see that one might assume that a "null string" and a "null pointer to an empty string" would have correspondence. The term "null" is used in quite an overloaded manner in casual conversation, and it can be easy to conflate the two.

Serve Laurijssen. They might as well just have chosen to let the string functions do nothing when being passed NULL. Keith Thompson. The correct term is "null pointer". It expands to an implementation-defined "null pointer constant". A "null pointer constant" and a "null pointer" are two very different things; the former is a construct that can appear in a C source file, and the latter is a value that can exist during execution of a program.

You typically use a null pointer constant to obtain a null pointer at run time which is why the name "null pointer constant" contains the phrase "null pointer" , but it can be important to keep the distinction in mind. A literal 0 is by definition a null pointer constant. A null pointer value may or may not be represented as all-bits-zero.

Section 5 of the comp. This is something. Therefore, we must do this. Stephen Sprunk. That might be considered reasonable, depending on who you ask. It was an eye-opening experience for me about assuming what's portable in C.

Luckily for me, I encountered this on my very first program okay, so my "hello world" used sockets and Motif, but still I'd prefer a happy medium -- a debug build that assert ed whenever I did something stupid, but also a release build that would make an attempt to do something sane and thus not crash on the user S -- Stephen Sprunk "God does not play dice.

Default User. I dont know exactly what the standard says, but at least it was decided at some point that strcpy does not accept NULL or at the very least does not have to. We are discussing strlen. The standard wording for that has been posted. Some other string functions may generate a different discussion. What does "do nothing" mean to you? No, strlen expected a pointer to a string as an argument.

And a null pointer does not point to a string. SM Ryan. Is it that strlen function can't handle NULL pointers? No, it doesn't. You can define your own string length function which does. When I'm developing I use the debug library. Gordon Burditt. Example: the first argument of strtok. Barry Schwarz. Yes but you can't call it strlen if it has external linkage since that name is reserved.