warning: the use of mktemp' is dangerous, better use mkstemp' or `mkdtemp'

[toffaletti]

Using swift:latest docker image I see this warning still. However, it seems like it should have been addressed back in Dec of 2020: #2927

I'm using the docker image created by this Dockerfile: https://github.com/swiftlang/swift-docker/blob/01bc0e265e8dca6381d801b76762ada6836afb69/6.0/ubuntu/24.04/Dockerfile

root@56a5c7b80758:/code# swift --version
Swift version 6.0.3 (swift-6.0.3-RELEASE)
Target: x86_64-unknown-linux-gnu
root@56a5c7b80758:/code# strings /usr/lib/swift_static/linux/libFoundationEssentials.a | grep mktemp
mktemp
root@56a5c7b80758:/code# strings /usr/lib/swift_static/linux/libFoundationEssentials.a | grep mkstemp
root@56a5c7b80758:/code#

root@56a5c7b80758:/code# strings /usr/lib/swift/linux/libFoundationEssentials.so | grep mktemp
mktemp
mktemp
root@56a5c7b80758:/code# strings /usr/lib/swift/linux/libFoundationEssentials.so | grep mkstemp
root@56a5c7b80758:/code#

swift build --static-swift-stdlib
Building for debugging...
/usr/lib/swift_static/linux/libFoundationEssentials.a(Data+Writing.swift.o):_ThreadLocal.swift.o:function $s20FoundationEssentials19createTemporaryFile33_FC9EC52B075D2ACCFF86F1C9F84293BELL2at6inPath6prefix7optionss5Int32V_SStSS_AA0Q5OrURLOSSAA4DataV14WritingOptionsVtKFTf4nnnd_n:(.text+0x2122): warning: the use of `mktemp' is dangerous, better use `mkstemp' or `mkdtemp'
/usr/lib/swift_static/linux/libFoundationEssentials.a(Data+Writing.swift.o):_ThreadLocal.swift.o:function $s20FoundationEssentials19createTemporaryFile33_FC9EC52B075D2ACCFF86F1C9F84293BELL2at6inPath6prefix7optionss5Int32V_SStSS_AA0Q5OrURLOSSAA4DataV14WritingOptionsVtKFTf4nnnd_n:(.text+0x21b8): warning: the use of `mktemp' is dangerous, better use `mkstemp' or `mkdtemp'
/usr/lib/swift_static/linux/libFoundationEssentials.a(Data+Writing.swift.o):_ThreadLocal.swift.o:function $s20FoundationEssentials19createTemporaryFile33_FC9EC52B075D2ACCFF86F1C9F84293BELL2at6inPath6prefix7optionss5Int32V_SStSS_AA0Q5OrURLOSSAA4DataV14WritingOptionsVtKFTf4nnnd_n:(.text+0x21f5): warning: the use of `mktemp' is dangerous, better use `mkstemp' or `mkdtemp'
/usr/lib/swift_static/linux/libFoundationEssentials.a(Data+Writing.swift.o):_ThreadLocal.swift.o:function $s20FoundationEssentials19createTemporaryFile33_FC9EC52B075D2ACCFF86F1C9F84293BELL2at6inPath6prefix7optionss5Int32V_SStSS_AA0Q5OrURLOSSAA4DataV14WritingOptionsVtKFTf4nnnd_n:(.text+0x2286): warning: the use of `mktemp' is dangerous, better use `mkstemp' or `mkdtemp'
/usr/lib/swift_static/linux/libFoundationEssentials.a(Data+Writing.swift.o):_ThreadLocal.swift.o:function $s20FoundationEssentials19createTemporaryFile33_FC9EC52B075D2ACCFF86F1C9F84293BELL2at6inPath6prefix7optionss5Int32V_SStSS_AA0Q5OrURLOSSAA4DataV14WritingOptionsVtKFTf4nnnd_n:(.text+0x22f1): warning: the use of `mktemp' is dangerous, better use `mkstemp' or `mkdtemp'

[toffaletti]

I verified the change is in the release/6.0 branch which seems to be where 6.0.3 is supposed to be tagged from:

swift-corelibs-foundation/Sources/Foundation/NSPathUtilities.swift

Line 684 in 26a599c

let fd = mkstemp(buffer.baseAddress!)

[toffaletti]

OK, I found the usage of mktemp, this issue should be moved to swift-foundation:

https://github.com/swiftlang/swift-foundation/blob/e9d59b6065ad909fee15f174bd5ca2c580490388/Sources/FoundationEssentials/Data/Data%2BWriting.swift#L173

[parkera]

There is an explanation in the source of why this doesn't work for us:

        // The warning diligently tells us we shouldn't be using mktemp() because blindly opening the returned path opens us up to a TOCTOU race. However, in this case, we're being careful by doing O_CREAT|O_EXCL and repeating, just like the implementation of mkstemp.
        // Furthermore, we can't compatibly switch to mkstemp() until we have the ability to set fchmod correctly, which requires the ability to query the current umask, which we don't have. (22033100)