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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal>I’m trying to understand why using a local memcpy with LTO results in a “multiple definition” error. <o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>I have an local (optimized) mempy.c (clearly simplified!):<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>void* memcpy(void* dest, const void* src, unsigned int count) {<o:p></o:p></p><p class=MsoNormal> return 0;<o:p></o:p></p><p class=MsoNormal>}<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>void* __aeabi_memcpy(void *dest, const void *src, unsigned int size) {<o:p></o:p></p><p class=MsoNormal> return memcpy(dest,src,size);<o:p></o:p></p><p class=MsoNormal>}<o:p></o:p></p><p class=MsoNormal>---<o:p></o:p></p><p class=MsoNormal>I also have a simple main.c to test it out (also simplified):<o:p></o:p></p><p class=MsoNormal>#include <stdio.h><o:p></o:p></p><p class=MsoNormal>#include <string.h><o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>struct {<o:p></o:p></p><p class=MsoNormal> char name[40];<o:p></o:p></p><p class=MsoNormal>} person;<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>char myname[] = "abcd";<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>int main ()<o:p></o:p></p><p class=MsoNormal>{<o:p></o:p></p><p class=MsoNormal> memcpy ( person.name, myname, strlen(myname)+1 );<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal> printf ("name :%s\n", person.name );<o:p></o:p></p><p class=MsoNormal> return 0;<o:p></o:p></p><p class=MsoNormal>}<o:p></o:p></p><p class=MsoNormal>---<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>During compilation with:<o:p></o:p></p><p class=MsoNormal>clang -O0 memcpy.c -o memcpy.o -c<o:p></o:p></p><p class=MsoNormal>ar cr memcpy.a memcpy.o<o:p></o:p></p><p class=MsoNormal>clang –O0 -o memcpyTest.exe -flto -static main.c memcpy.a <o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>I get a multiple definition of memcpy error. Now building it with –fno-builtin works fine. I’m trying to understand what is happening behind the scenes that requires my use of –fno-builtin (or –Wl,--allow-multiple-definitions). Did the backend put in references to libc that are trying to get resolved before loading the optimized archive? I also notice that replacing memcpy.a with memcpy.o works just fine as well. Can someone give me some insight?<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>I’ve found <a href="https://gcc.gnu.org/bugzilla/show_bug.cgi?id=55994">this discussion</a> regarding GCC that seems to center around the same issue. <o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Daniel <o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>--<o:p></o:p></p><p class=MsoNormal>Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p></div></body></html>