Hi Gregor,
nitish
main.go
node.c
node.h
I compiled using 'go build -v -x main.go'
But if my cgo directive is defined in main.go, this should have compiled
successfully..right? But it fails with the following whereas 'go build -v
-x' works fine.
/tmp/go-build439591561/b001/_x002.o: In function
`_cgo_5637ad3d75e4_Cfunc_load_pattern_db':
/tmp/go-build/cgo-gcc-prolog:86: undefined reference to `load_pattern_db'
collect2: error: ld returned 1 exit status
package main
//#include <stdlib.h>
//#include "node.h"
import "C"
import (
"fmt"
_ "fmt"
"os"
"path"
"unsafe"
)
Please let me know what am I missing here?
Thanks,
Nitish
On Wed, Mar 18, 2020 at 7:20 PM Nitish Saboo <nitish.sabo...@gmail.com>
wrote:
> Hi Gregor,
>
> Got your point.Thank you for your response.
> That explains why the binaries have different names post compilation.
>
> Thanks,
> Nitish
>
>
> On Wed, Mar 18, 2020 at 7:06 PM Gregor Best <b...@pferdewetten.de> wrote:
>
>> Hi,
>>
>> In both `go build main.go`-examples, you tell the compiler to _only_
>> build `main.go`.
>>
>> In your first example, `main.go` probably imports both `util` and `lib`
>> (you might want to give them less generic names by the way). The go
>> compiler thus knows "to build `main.go`, I need to build both `util` and
>> `lib` and link them in".
>>
>> In the second example, it has no way of knowing where `load_pattern_db`
>> comes from, since you didn't tell it to compile a file that defines that
>> function.
>>
>> The examples where you omit the `main.go` tell the compiler "build the
>> package in this directory", which includes all `.go`-files in the
>> directory. `node.c` and `node.h` are likely built because of `cgo`
>> directives in `a.go`.
>>
>> The compiler and linker did exactly as you told them to.
>> On 18.03.20 14:17, Nitish Saboo wrote:
>>
>> Hi,
>>
>>
>>
>> *Case 1 ---------- *
>> I have a project called 'nitish' where the folder structure looks like
>> the following:
>>
>> nitish
>> main.go
>> util
>> util.go
>> lib
>> node.c
>> node.h
>> a.go
>>
>> When I try compiling this project in the following ways:
>>
>> 1) go build -v - x
>>
>> >> This creates a binary called 'nitish'
>>
>> 2) go build -v - x main.go
>>
>> >> This creates a binary called 'main'
>>
>> ldd output of both the binaries is the same.
>>
>>
>>
>> *Case 2 ----------*
>>
>> Now, when I restructure the project 'nitish' in the following manner:
>>
>> nitish
>> main.go
>> util.go
>> node.c
>> node.h
>> a.go
>>
>> When I try compiling this project in the following ways:
>>
>> 1) go build -v - x
>>
>> >> This creates a binary called 'nitish'
>>
>> 2) go build -v - x main.go
>>
>> >> This error out with the following:
>>
>> /tmp/go-build074530518/b001/_x002.o: In function
>> `_cgo_8eab385aa676_Cfunc_load_pattern_db':
>> /tmp/go-build/cgo-gcc-prolog:86: undefined reference to `load_pattern_db'
>> collect2: error: ld returned 1 exit status
>>
>>
>> 1) In Case 1, why the binaries are created with different names though
>> both the binaries have the same 'ldd output' and work the same manner?
>>
>> 2) Why we see an error with the command 'go build -v - x main.go' in Case
>> 2 but not in Case 1?
>>
>> Thanks,
>> Nitish
>>
>> --
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>>
>> --
>> --
>> Gregor Best
>> b...@pferdewetten.de
>>
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>>
>
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