binaryfiles - how does gcc compiler produces machine/processor independent binary? -

-

my question bit dummy, had question in mind.

how gcc @ compile time determines target machine/processor getting build-ed ?

are instructions generated gcc/g++ target system independent ?

for example have x86_64 machine intel based , amd based , motorola based system etc...

do processors have same instruction set , opcode associated ?

if not machine-code/binary generated gcc have kind of runtime check ?

thanks in advance answer.

this bit complicated. depends on how gcc configured , compiled during installation. on ubuntu 16.04 x64 system there gcc installation.

if in terminal type gcc -v, i'll --target=x86_64-linux-gnu, means gcc produce code x64 linux. --host=x86_64-linux-gnu means gcc x64 linux application. more of @ link.

another useful output @ --with-multilib-list=m32,m64,mx32 - means compile default 64bit application 2 types of 32bit applications (-m32 , -mx32).

last not least --with-tune=generic, means apps compiled generic x64 platform , user should able run them anywhere on x64 linux box.

there 2 options override - -march , -mtune. arch option tell compiler use intruction specific given cpu. tune tune code generation fit best given cpu. cpu either specific platform (like, say, sandybridge), generic platform (usually default) or native, gcc during compilation check host cpu , perform code generation/tuning it.

last set of option covers setting fpu - select unit use (x87 or sse2+), instruction set (sse2, 3, 4, avx) etc. more link.


Comments

Post a Comment

Popular posts from this blog

Spring Boot + JPA + Hibernate: Unable to locate persister -

-
i trying work entity inside request method of spring boot application. entity in project , pom.xml has dependencies it. why error message?: org.hibernate.unknownentitytypeexception: unable locate persister: com.ric.bill.model.bs.par package com.ric.web; import java.util.concurrent.atomic.atomiclong; import javax.persistence.entitymanager; import javax.persistence.persistencecontext; import net.sf.ehcache.cachemanager; import net.sf.ehcache.management.cache; import net.sf.ehcache.management.cachestatistics; import org.hibernate.stat.statistics; import org.springframework.beans.factory.annotation.autowired; import org.springframework.boot.autoconfigure.domain.entityscan; import org.springframework.cache.annotation.enablecaching; import org.springframework.transaction.annotation.enabletransactionmanagement; import org.springframework.transaction.annotation.propagation; import org.springframework.transaction.annotation.transactional; import org.springframework.web.bind.annotati
Read more

go - Golang: panic: runtime error: invalid memory address or nil pointer dereference using bufio.Scanner -

-
i implementing go program uses bufio.scanner , bufio.writer have packaged code follows package main import ( "fmt" "player/command" "strings" ) func main() { //enter code here. read input stdin. print output stdout commands.scanner.scan() { //scan new line , send comand variable check command exist or not input := strings.split(strings.trim(commands.scanner.text(), " "), " ") command := input[0] if command == "" { fmt.printf("$ %s:", commands.pwd) continue } if !commands.commands[command] { commands.throwerror("cannot recognize input.") } else { commands.execute(command, input[1:], nil) } fmt.printf("$ %s:", commands.pwd) } } i using init.go file in main package follows package main import ( "flag" "player/sourc
Read more

c - double free or corruption (fasttop) -

-
this code reads null terminated string file (file containing null terminated strings & should provide index wanted string). error: *** error in `./main': double free or corruption (fasttop): 0x090a4a80 *** aborted code: char *tmp_realloc=null; char *sstring=null; int i=1; /*set file pointer point string*/ fseek(fh,index,seek_set); sstring=(char*)malloc(sizeof(char)); if(sstring == null) return null; tmp_realloc=sstring; while( (*(sstring+i-1)=(char)fgetc((file*)fh)) != 0x0 ) { /*reallocate more memory*/ tmp_realloc=(char*)realloc((char*)sstring,++i); /*if not same address copy old new & set old point new*/ if(tmp_realloc != sstring){ strcpy((char*)tmp_realloc,(char*)sstring); free(sstring); sstring=tmp_realloc; } } could tell me pointer causing issue (& reason) ? remove part /*if not same address copy old new & set old point new*/ if(tmp_realloc != sstring){ strc
Read more