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cmd/cgo: better error message when a different gcc is needed on Windows #21024

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pkch opened this issue Jul 15, 2017 · 11 comments
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cmd/cgo: better error message when a different gcc is needed on Windows #21024

pkch opened this issue Jul 15, 2017 · 11 comments
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FrozenDueToAge NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. WaitingForInfo Issue is not actionable because of missing required information, which needs to be provided.
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Go1.10

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@pkch
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pkch commented Jul 15, 2017

When building go from source on Windows, the gcc needs to support input from stdin; the exact command run is:

$ gcc -E -dM -xc -m64 -I $WORK\runtime\cgo\_obj\ -g -O2 -Wall -Werror - <<EOF

something something

EOF

Apparently, not all gcc for Windows handle reading from stdin correctly; mine (realgcc) didn't, and I got this very brief error message when running tests with all.bat:

# runtime/cgo
realgcc.exe: fatal error: no input files
compilation terminated.

It would be nice to have an error message suggesting to use a different gcc (and ideally, recommending a particular one).
@pkch pkch changed the title Better error message needed when a different gcc is needed on Windows Better error message when a different gcc is needed on Windows Jul 15, 2017
@ianlancetaylor ianlancetaylor changed the title Better error message when a different gcc is needed on Windows cmd/cgo: better error message when a different gcc is needed on Windows Jul 15, 2017
@ianlancetaylor
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Which version of Go?

In current versions of Go the comment that is executed is not precisely the command that is printed. cgo actually writes the input to a file, and passes the file to the compiler. That should have happened in this case. That was fixed in the Go 1.7 release.

@pkch
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pkch commented Jul 15, 2017

I was building from master, and pointed go bootstrap path to the newest ( go 1.8.3) binary that I just downloaded.

@ianlancetaylor
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Can you attach the complete output from cgo with the -debug-gcc option?

Note that the command that cgo displays is not the exact command that it executes. So while clearly something is wrong, I don't yet see how the problem could be passing standard input to the compiler. See the run function in cmd/cgo/util.go.

@pkch
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pkch commented Jul 15, 2017

IIUC, I don't get to the point of running cgo; the error happens when building cgo:

C:\Users\max\Downloads\go\src>..\bin\go build -x -v runtime/cgo
WORK=C:\Users\max\AppData\Local\Temp\go-build037782430
runtime/cgo
mkdir -p $WORK\runtime\cgo\_obj\
mkdir -p $WORK\runtime\
cd C:\Users\max\Downloads\go\src\runtime\cgo
CGO_LDFLAGS="-g" "-O2" "C:\\Users\\max\\Downloads\\go\\pkg\\tool\\windows_amd64\\cgo.exe" -objdir "C:\\Users\\max\\AppData\\Local\\Temp\\go-build037782430\\runtime\\cgo\\_obj\\" -importpath runtime/cgo -import_runtime_cgo=false -import_syscall=false -- -I "C:\\Users\\max\\AppData\\Local\\Temp\\go-build037782430\\runtime\\cgo\\_obj\\" -g -O2 -Wall -Werror cgo.go                                                                                                                               
# runtime/cgo
realgcc.exe: fatal error: no input files
compilation terminated.

Should I add any options to this to provide more details? (realgcc.exe is what's gcc is linked to on my computer.)

@ianlancetaylor
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That is running cgo, not building cgo. It is running the program C:\\Users\\max\\Downloads\\go\\pkg\\tool\\windows_amd64\\cgo.exe with various environment variables and options.

A simple thing that may help is to temporarily replace realgcc.exe with a program that just dumps its arguments, such as the echo program if you have that. That will shows us exactly how the compiler is being invoked.

@pkch
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pkch commented Jul 16, 2017

This is what I'm getting after replacing gcc (which came with Haskell distro, and seems to be mingw gcc) with echo:

C:\Users\max\Downloads\go\src>..\bin\go build -x -v runtime/cgo
WORK=C:\Users\max\AppData\Local\Temp\go-build247954586
runtime/cgo
mkdir -p $WORK\runtime\cgo\_obj\
mkdir -p $WORK\runtime\
cd C:\Users\max\Downloads\go\src\runtime\cgo
CGO_LDFLAGS="-g" "-O2" "C:\\Users\\max\\Downloads\\go\\pkg\\tool\\windows_amd64\\cgo.exe" -objdir "C:\\Users\\max\\AppData\\Local\\Temp\\go-build247954586\\runtime\\cgo\\_obj\\" -importpath runtime/cgo -import_runtime_cgo=false -import_syscall=false -- -I "C:\\Users\\max\\AppData\\Local\\Temp\\go-build247954586\\runtime\\cgo\\_obj\\" -g -O2 -Wall -Werror cgo.go
cd $WORK
gcc -fdebug-prefix-map=a=b -c trivial.c
gcc -gno-record-gcc-switches -c trivial.c
cd $WORK\runtime\cgo\_obj
gcc -I "C:\\Users\\max\\Downloads\\go\\src\\runtime\\cgo" -m64 -mthreads -fmessage-length=0 "-fdebug-prefix-map=C:\\Users\\max\\AppData\\Local\\Temp\\go-build247954586=/tmp/go-build" -gno-record-gcc-switches -I "C:\\Users\\max\\AppData\\Local\\Temp\\go-build247954586\\runtime\\cgo\\_obj\\" -g -O2 -Wall -Werror -o "C:\\Users\\max\\AppData\\Local\\Temp\\go-build247954586\\runtime\\cgo\\_obj\\_cgo_export.o" -c _cgo_export.c
# runtime/cgo
-I runtime\cgo -m64 -mthreads -fmessage-length=0 -fdebug-prefix-map=C:\Users\max\AppData\Local\Temp\go-build247954586=/tmp/go-build -gno-record-gcc-switches -I $WORK\runtime\cgo\_obj\ -g -O2 -Wall -Werror -o $WORK\runtime\cgo\_obj\_cgo_export.o -c _cgo_export.c
gcc -I "C:\\Users\\max\\Downloads\\go\\src\\runtime\\cgo" -m64 -mthreads -fmessage-length=0 "-fdebug-prefix-map=C:\\Users\\max\\AppData\\Local\\Temp\\go-build247954586=/tmp/go-build" -gno-record-gcc-switches -I "C:\\Users\\max\\AppData\\Local\\Temp\\go-build247954586\\runtime\\cgo\\_obj\\" -g -O2 -Wall -Werror -o "C:\\Users\\max\\AppData\\Local\\Temp\\go-build247954586\\runtime\\cgo\\_obj\\cgo.cgo2.o" -c cgo.cgo2.c
# runtime/cgo
-I runtime\cgo -m64 -mthreads -fmessage-length=0 -fdebug-prefix-map=C:\Users\max\AppData\Local\Temp\go-build247954586=/tmp/go-build -gno-record-gcc-switches -I $WORK\runtime\cgo\_obj\ -g -O2 -Wall -Werror -o $WORK\runtime\cgo\_obj\cgo.cgo2.o -c cgo.cgo2.c
cd C:\Users\max\Downloads\go\src\runtime\cgo
gcc -I "C:\\Users\\max\\Downloads\\go\\src\\runtime\\cgo" -m64 -mthreads -fmessage-length=0 "-fdebug-prefix-map=C:\\Users\\max\\AppData\\Local\\Temp\\go-build247954586=/tmp/go-build" -gno-record-gcc-switches -I "C:\\Users\\max\\AppData\\Local\\Temp\\go-build247954586\\runtime\\cgo\\_obj\\" -g -O2 -Wall -Werror -o "C:\\Users\\max\\AppData\\Local\\Temp\\go-build247954586\\runtime\\cgo\\_obj\\gcc_context.o" -c gcc_context.c
# runtime/cgo
-I runtime\cgo -m64 -mthreads -fmessage-length=0 -fdebug-prefix-map=C:\Users\max\AppData\Local\Temp\go-build247954586=/tmp/go-build -gno-record-gcc-switches -I $WORK\runtime\cgo\_obj\ -g -O2 -Wall -Werror -o $WORK\runtime\cgo\_obj\gcc_context.o -c gcc_context.c
gcc -I "C:\\Users\\max\\Downloads\\go\\src\\runtime\\cgo" -m64 -mthreads -fmessage-length=0 "-fdebug-prefix-map=C:\\Users\\max\\AppData\\Local\\Temp\\go-build247954586=/tmp/go-build" -gno-record-gcc-switches -I "C:\\Users\\max\\AppData\\Local\\Temp\\go-build247954586\\runtime\\cgo\\_obj\\" -g -O2 -Wall -Werror -o "C:\\Users\\max\\AppData\\Local\\Temp\\go-build247954586\\runtime\\cgo\\_obj\\gcc_libinit_windows.o" -c gcc_libinit_windows.c
# runtime/cgo
-I runtime\cgo -m64 -mthreads -fmessage-length=0 -fdebug-prefix-map=C:\Users\max\AppData\Local\Temp\go-build247954586=/tmp/go-build -gno-record-gcc-switches -I $WORK\runtime\cgo\_obj\ -g -O2 -Wall -Werror -o $WORK\runtime\cgo\_obj\gcc_libinit_windows.o -c gcc_libinit_windows.c
gcc -I "C:\\Users\\max\\Downloads\\go\\src\\runtime\\cgo" -m64 -mthreads -fmessage-length=0 "-fdebug-prefix-map=C:\\Users\\max\\AppData\\Local\\Temp\\go-build247954586=/tmp/go-build" -gno-record-gcc-switches -I "C:\\Users\\max\\AppData\\Local\\Temp\\go-build247954586\\runtime\\cgo\\_obj\\" -g -O2 -Wall -Werror -o "C:\\Users\\max\\AppData\\Local\\Temp\\go-build247954586\\runtime\\cgo\\_obj\\gcc_util.o" -c gcc_util.c
# runtime/cgo
-I runtime\cgo -m64 -mthreads -fmessage-length=0 -fdebug-prefix-map=C:\Users\max\AppData\Local\Temp\go-build247954586=/tmp/go-build -gno-record-gcc-switches -I $WORK\runtime\cgo\_obj\ -g -O2 -Wall -Werror -o $WORK\runtime\cgo\_obj\gcc_util.o -c gcc_util.c
gcc -I "C:\\Users\\max\\Downloads\\go\\src\\runtime\\cgo" -m64 -mthreads -fmessage-length=0 "-fdebug-prefix-map=C:\\Users\\max\\AppData\\Local\\Temp\\go-build247954586=/tmp/go-build" -gno-record-gcc-switches -I "C:\\Users\\max\\AppData\\Local\\Temp\\go-build247954586\\runtime\\cgo\\_obj\\" -g -O2 -Wall -Werror -o "C:\\Users\\max\\AppData\\Local\\Temp\\go-build247954586\\runtime\\cgo\\_obj\\gcc_windows_amd64.o" -c gcc_windows_amd64.c
# runtime/cgo
-I runtime\cgo -m64 -mthreads -fmessage-length=0 -fdebug-prefix-map=C:\Users\max\AppData\Local\Temp\go-build247954586=/tmp/go-build -gno-record-gcc-switches -I $WORK\runtime\cgo\_obj\ -g -O2 -Wall -Werror -o $WORK\runtime\cgo\_obj\gcc_windows_amd64.o -c gcc_windows_amd64.c
gcc -I "C:\\Users\\max\\Downloads\\go\\src\\runtime\\cgo" -m64 -mthreads -fmessage-length=0 "-fdebug-prefix-map=C:\\Users\\max\\AppData\\Local\\Temp\\go-build247954586=/tmp/go-build" -gno-record-gcc-switches -I "C:\\Users\\max\\AppData\\Local\\Temp\\go-build247954586\\runtime\\cgo\\_obj\\" -g -O2 -Wall -Werror -o "C:\\Users\\max\\AppData\\Local\\Temp\\go-build247954586\\runtime\\cgo\\_obj\\gcc_amd64.o" -c gcc_amd64.S
# runtime/cgo
-I runtime\cgo -m64 -mthreads -fmessage-length=0 -fdebug-prefix-map=C:\Users\max\AppData\Local\Temp\go-build247954586=/tmp/go-build -gno-record-gcc-switches -I $WORK\runtime\cgo\_obj\ -g -O2 -Wall -Werror -o $WORK\runtime\cgo\_obj\gcc_amd64.o -c gcc_amd64.S
cd $WORK\runtime\cgo\_obj
gcc -I "C:\\Users\\max\\Downloads\\go\\src\\runtime\\cgo" -m64 -mthreads -fmessage-length=0 "-fdebug-prefix-map=C:\\Users\\max\\AppData\\Local\\Temp\\go-build247954586=/tmp/go-build" -gno-record-gcc-switches -I "C:\\Users\\max\\AppData\\Local\\Temp\\go-build247954586\\runtime\\cgo\\_obj\\" -g -O2 -Wall -Werror -o "C:\\Users\\max\\AppData\\Local\\Temp\\go-build247954586\\runtime\\cgo\\_obj\\_cgo_main.o" -c _cgo_main.c
# runtime/cgo
-I runtime\cgo -m64 -mthreads -fmessage-length=0 -fdebug-prefix-map=C:\Users\max\AppData\Local\Temp\go-build247954586=/tmp/go-build -gno-record-gcc-switches -I $WORK\runtime\cgo\_obj\ -g -O2 -Wall -Werror -o $WORK\runtime\cgo\_obj\_cgo_main.o -c _cgo_main.c
cd C:\Users\max\Downloads\go\src\runtime\cgo
gcc -I "C:\\Users\\max\\Downloads\\go\\src\\runtime\\cgo" -m64 -mthreads -fmessage-length=0 "-fdebug-prefix-map=C:\\Users\\max\\AppData\\Local\\Temp\\go-build247954586=/tmp/go-build" -gno-record-gcc-switches -o "C:\\Users\\max\\AppData\\Local\\Temp\\go-build247954586\\runtime\\cgo\\_obj\\_cgo_.o" "C:\\Users\\max\\AppData\\Local\\Temp\\go-build247954586\\runtime\\cgo\\_obj\\_cgo_main.o" "C:\\Users\\max\\AppData\\Local\\Temp\\go-build247954586\\runtime\\cgo\\_obj\\_cgo_export.o" "C:\\Users\\max\\AppData\\Local\\Temp\\go-build247954586\\runtime\\cgo\\_obj\\cgo.cgo2.o" "C:\\Users\\max\\AppData\\Local\\Temp\\go-build247954586\\runtime\\cgo\\_obj\\gcc_context.o" "C:\\Users\\max\\AppData\\Local\\Temp\\go-build247954586\\runtime\\cgo\\_obj\\gcc_libinit_windows.o" "C:\\Users\\max\\AppData\\Local\\Temp\\go-build247954586\\runtime\\cgo\\_obj\\gcc_util.o" "C:\\Users\\max\\AppData\\Local\\Temp\\go-build247954586\\runtime\\cgo\\_obj\\gcc_windows_amd64.o" "C:\\Users\\max\\AppData\\Local\\Temp\\go-build247954586\\runtime\\cgo\\_obj\\gcc_amd64.o" -g -O2
# runtime/cgo
-I runtime\cgo -m64 -mthreads -fmessage-length=0 -fdebug-prefix-map=C:\Users\max\AppData\Local\Temp\go-build247954586=/tmp/go-build -gno-record-gcc-switches -o $WORK\runtime\cgo\_obj\_cgo_.o $WORK\runtime\cgo\_obj\_cgo_main.o $WORK\runtime\cgo\_obj\_cgo_export.o $WORK\runtime\cgo\_obj\cgo.cgo2.o $WORK\runtime\cgo\_obj\gcc_context.o $WORK\runtime\cgo\_obj\gcc_libinit_windows.o $WORK\runtime\cgo\_obj\gcc_util.o $WORK\runtime\cgo\_obj\gcc_windows_amd64.o $WORK\runtime\cgo\_obj\gcc_amd64.o -g -O2
"C:\\Users\\max\\Downloads\\go\\pkg\\tool\\windows_amd64\\cgo.exe" -dynpackage cgo -dynimport "C:\\Users\\max\\AppData\\Local\\Temp\\go-build247954586\\runtime\\cgo\\_obj\\_cgo_.o" -dynout "C:\\Users\\max\\AppData\\Local\\Temp\\go-build247954586\\runtime\\cgo\\_obj\\_cgo_import.go" -dynlinker
# runtime/cgo
cannot parse $WORK\runtime\cgo\_obj\_cgo_.o as ELF, Mach-O or PE

@ianlancetaylor
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Thanks. Unfortunately, it looks like cgo breaks (unable to read _cgo_.o) before it reaches the point of failure. Perhaps you could use a script that echos the argument and then execs the real compiler.

@pkch
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pkch commented Jul 17, 2017

Sorry, Windows + cgo build system outsmarted me. However much I tried to trick them with a Windows batch files to echo the arguments (to a file or to screen) and compile, it still managed to hide everything up until the "no input files" error. I will try again some time.

I guess that it's better to just use the recommended gcc anyway, and I just noticed the warning about incompatibility with some other flavors of gcc.

@odeke-em
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Not a regression so I'll mark this for investigation during the Go1.10 cycle.

@odeke-em odeke-em added NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. WaitingForInfo Issue is not actionable because of missing required information, which needs to be provided. labels Jul 21, 2017
@odeke-em odeke-em added this to the Go1.10 milestone Jul 21, 2017
@alexbrainman
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Sorry, Windows + cgo build system outsmarted me. However much I tried to trick them with a Windows batch files to echo the arguments (to a file or to screen)

I always struggle with batch files. I would use Go to write such tool instead. You will need to invoke programs with redirected stdin/stdout/stderr, pass program parameters and print to the screen or file - Go should be fine for that.

Alex

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Timed out in state WaitingForInfo. Closing.

(I am just a bot, though. Please speak up if this is a mistake or you have the requested information.)

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