effect to systems satisfying one of the constraints
(see https://golang.org/pkg/go/build/#hdr-Build_Constraints for details about the constraint syntax).
For example:

	// #cgo CFLAGS: -DPNG_DEBUG=1
	// #cgo amd64 386 CFLAGS: -DX86=1
	// #cgo LDFLAGS: -lpng
	// #include <png.h>
	import "C"

Alternatively, CPPFLAGS and LDFLAGS may be obtained via the pkg-config tool
using a '#cgo pkg-config:' directive followed by the package names.

pkg syscall (windows-386), const CTRL_SHUTDOWN_EVENT ideal-int
pkg syscall (windows-amd64), const CTRL_CLOSE_EVENT = 2
pkg syscall (windows-amd64), const CTRL_CLOSE_EVENT ideal-int
pkg syscall (windows-amd64), const CTRL_LOGOFF_EVENT = 5
pkg syscall (windows-amd64), const CTRL_LOGOFF_EVENT ideal-int
pkg syscall (windows-amd64), const CTRL_SHUTDOWN_EVENT = 6
pkg syscall (windows-amd64), const CTRL_SHUTDOWN_EVENT ideal-int
pkg testing, method (*B) Cleanup(func())

-Encryption-S3-Sealed-Key":"IAAfAJiUMyw4aEq6j+dLDvYKHCYiE7oLA2mfuz==","X-Minio-Internal-Server-Side-Encryption-Seal-Algorithm":"DAREv2-HMAC-SHA256","content-type":"application/octet-stream"}},{"Bucket":"buck1","Name":"go_113/src/cmd/link/internal/amd64/asm.go","UserDef":{"X-Minio-Internal-Server-Side-Encryption-Iv":"NbQW52LzWCjtLkkUhjzI+VMY8E=","X-Minio-Internal-Server-Side-Encryption-S3-Kms-Key-Id":"my-minio-key","X-Minio-Internal-Server-Side-Encryption-S3-Kms-Sealed-Key":"IAAfANfPKAvqb75Ev5JU+...

            <li>Regex matching: {@code matches(${os.version}, '.*aws')}</li>
            <li>Complex condition: {@code ${os.name} == 'windows' && ${os.arch} != 'amd64' && inrange(${os.version}, '[10,)')}</li>
            <li>String length check: {@code length(${user.name}) > 5}</li>
            <li>Substring with version: {@code substring(${java.version}, 0, 3) == '1.8'}</li>

pkg syscall (windows-386), type SysProcAttr struct, ThreadAttributes *SecurityAttributes
pkg syscall (windows-amd64), type SysProcAttr struct, ProcessAttributes *SecurityAttributes
pkg syscall (windows-amd64), type SysProcAttr struct, ThreadAttributes *SecurityAttributes
pkg testing, func Init()
pkg testing, method (*B) ReportMetric(float64, string)

// generated by x86test -amd64
// DO NOT EDIT

#include "../../../../../runtime/textflag.h"

TEXT asmtest(SB),DUPOK|NOSPLIT,$0
	ADCB $7, AL                             // 1407
	ADCW $61731, AX                         // 661523f1
	ADCL $4045620583, AX                    // 15674523f1
	ADCQ $-249346713, AX                    // 4815674523f1
	ADCW $61731, (BX)                       // 66811323f1
	ADCW $61731, (R11)                      // 6641811323f1