>Submitter-Id: net >Originator: [EMAIL PROTECTED] >Organization: The Debian project >Confidential: no >Synopsis: Inlined strlen() could be smarter >Severity: non-critical >Priority: low >Category: optimization >Class: sw-bug >Release: 3.0 (Debian GNU/Linux) and HEAD 20010701 >Environment: System: Debian GNU/Linux (testing/unstable) Architecture: i686 host: i386-linux build: i386-linux target: i386-linux configured with: ../src/configure -v --enable-languages=c,c++,java,f77,proto,objc --prefix=/usr --infodir=/share/info --mandir=/share/man --enable-shared --with-gnu-as --with-gnu-ld --with-system-zlib --enable-long-long --enable-nls --without-included-gettext --disable-checking --enable-threads=posix --enable-java-gc=boehm --with-cpp-install-dir=bin --enable-objc-gc i386-linux >Description: [ Reported to the Debian BTS as report #86251. Please CC [EMAIL PROTECTED] on replies. Log of report can be found at http://bugs.debian.org/86251 ]
gcc -S -O2 on the file #include <string.h> size_t mystrlen(const char *s) { if (!s) { s = ""; } return strlen(s); } generates (on i386) .file "bug-86251.c" .section .rodata .LC0: .string "" .text .align 2 .p2align 2,,3 .globl mystrlen .type mystrlen,@function mystrlen: pushl %ebp movl %esp, %ebp pushl %edi movl 8(%ebp), %edi testl %edi, %edi je .L114 .L113: xorl %eax, %eax cld movl $-1, %ecx repnz scasb notl %ecx leal -1(%ecx), %eax movl (%esp), %edi leave ret .p2align 2,,3 .L114: movl $.LC0, %edi jmp .L113 .Lfe1: .size mystrlen,.Lfe1-mystrlen .ident "GCC: (GNU) 3.1 20010701 (experimental)" As you can see, strlen() is not optimised out in the !pat case. >How-To-Repeat: >Fix: