Memory Layout for ProcessCreating a ProcessA Simple ExampleObject FileSlide 5After Pass 1RelocationSlide 8CS 140 Lecture Notes: Linkers Slide 1Memory Layout for ProcessCode0∞DataStackCS 140 Lecture Notes: Linkers Slide 2Creating a ProcessCode0∞DataStack101010101010101010101010101010101010101010101010ccx.c x.s as x.o101010101010101010101010101010101010101010101010ccy.c y.s as y.o101010101010101010101010101010101010101010101010ccz.c z.s as z.o101010101010101010101010101010101010101010101010SourceCodeAssemblyCodeObjectCodeExecutablea.outCompiler Assembler Linker LoaderldOSCS 140 Lecture Notes: Linkers Slide 3A Simple Exampleextern float sin();extern printf(), scanf();main() { double x, result; printf("Type number: "); scanf("%f", &x); result = sin(x); printf("Sine is %f\n", result);}extern float sin();extern printf(), scanf();main() { double x, result; printf("Type number: "); scanf("%f", &x); result = sin(x); printf("Sine is %f\n", result);}main.cint printf(char *fmt, ...) { ...}int scanf(char *fmt, ...) { ...}int printf(char *fmt, ...) { ...}int scanf(char *fmt, ...) { ...}stdio.cdouble sin(double x) { static double res, lastx; if (x != lastx) { lastx = x; … compute sin(x) … } return res;}double sin(double x) { static double res, lastx; if (x != lastx) { lastx = x; … compute sin(x) … } return res;}math.cCS 140 Lecture Notes: Linkers Slide 4Object Fileextern float sin();extern printf(), scanf();main() { double x, result; printf("Type number: "); scanf("%f", &x); result = sin(x); printf("Sine is %f\n", result);}extern float sin();extern printf(), scanf();main() { double x, result; printf("Type number: "); scanf("%f", &x); result = sin(x); printf("Sine is %f\n", result);}main.c main.o20324056...call printf...call scanf...call sin...call printfdef: main@T:0ref: printf@T:20, T:56ref: scanf@T:32ref: sin@T:40...call printf...call scanf...call sin...call printfdef: main@T:0ref: printf@T:20, T:56ref: scanf@T:32ref: sin@T:40text segmentsymbolsrelocationCS 140 Lecture Notes: Linkers Slide 5Object Filedouble sin(double x) { static double res, lastx; if (x != lastx) { lastx = x; … compute sin(x) … } return res;}double sin(double x) { static double res, lastx; if (x != lastx) { lastx = x; … compute sin(x) … } return res;}math.c math.o 8 20204 0 8...load lastx...store lastx...load resres:lastx:def: sin@T:0def: lastx@D:0def: res@D:8ref: lastx@T:8, T:20ref: res@T:204...load lastx...store lastx...load resres:lastx:def: sin@T:0def: lastx@D:0def: res@D:8ref: lastx@T:8, T:20ref: res@T:204text segmentdata segmentrelocationsymbolsCS 140 Lecture Notes: Linkers Slide 6After Pass 1main.o text064276700math.o textstdio.o textmath.o data708stdio.o data836main: 0sin: 64lastx: 700result: 708printf: 314scanf: 508Memory map: Symbol table:CS 140 Lecture Notes: Linkers Slide 7Relocationtext segment in main.o40...call 0...ref: sin@T:40relocation record in main.osin: 64symbol tabletext segment in a.out40...call 64...CS 140 Lecture Notes: Linkers Slide
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