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Banned C standard library functions in Git source code

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Re: Banned C standard library functions in Git source code

#51

Post by saagarjha »

gus_massa wrote: post #43
jcl wrote: post #33

Looks like the second vsprintf definition should be "BANNED(vsprintf)", not "BANNED(sprintf)". Not that it matters much, as it only affects the error message.

Nice catch! You can send a "PR", but note that they have their own custom "PR" procedure, not the standard "PR" procedure in GitHub. > Git Source Code Mirror - This is a publish-only repository and all pull requests are ignored. Please follow https://github.com/git/git/blob/master/Documentation/Submitt... procedure for any of your improvements.

Aside: GitHub’s refusal to provide a feature to close pull requests for mirrors is utterly ridiculous since it requires that people (or bots) go around and disable pull requests and point people to the patch submission process.

Re: Banned C standard library functions in Git source code

#52

Post by susam »

saagarjha wrote: post #35
alister wrote: post #26

I'm glad to see that setjmp() and longjmp() are still allowed. I'm just kidding by the way. For those C programmers who haven't encountered these before, it is a powerful way to do a "goto" in C. Powerful in the sense that you can jump anywhere, not limited to the same function. If it's used at all these days, it's used for exception handling. More info: https://en.wikipedia.org/wiki/Setjmp.h

I see zero use of those in the codebase, so perhaps they should be banned too. Or maybe they’re not on this list because nobody was using them already?

I have worked in large code bases (RSA NetWitness, Oracle Database, etc.) where setjmp/longjmp were used to create macros for exception handling using TRY-CATCH-ENDTRY blocks in C.

Re: Banned C standard library functions in Git source code

#53

Post by yjftsjthsd-h »

gus_massa wrote: post #43
jcl wrote: post #33

Looks like the second vsprintf definition should be "BANNED(vsprintf)", not "BANNED(sprintf)". Not that it matters much, as it only affects the error message.

Nice catch! You can send a "PR", but note that they have their own custom "PR" procedure, not the standard "PR" procedure in GitHub. > Git Source Code Mirror - This is a publish-only repository and all pull requests are ignored. Please follow https://github.com/git/git/blob/master/Documentation/Submitt... procedure for any of your improvements.

> not the standard "PR" procedure in GitHub

If it is specific to one implementation, then it is not standard, pretty much by definition.

Re: Banned C standard library functions in Git source code

#54

Post by tlb »

zsrxx wrote: post #38
adamnemecek wrote: post #27

Earlier quoted context omitted.

Like essentially all C programs.

What's a good library for this kind of boilerplate? A lightweight one if possible, i.e. not fucking glib

There are far too many. APR is a solid choice -- very portable, well-tested, and fast. It uses memory pools a lot, which work well for many styles but not everything.

See https://apr.apache.org/docs/apr/1.7/modules.html

Re: Banned C standard library functions in Git source code

#55

Post by b55c63a4 »

For context, this header file was introduced during the period of Microsoft's acquisition of GitHub.

Git's banned.h roughly approximates the banned functions according to Microsoft's Security Development Lifecycle: https://docs.microsoft.com/en-us/previous-versions/bb288454(...

It seems Microsoft once published their own banned.h, but this file is not readily available from the MSDN anymore.

Re: Banned C standard library functions in Git source code

#56

Post by slovenlyrobot »

alister wrote: post #26

I'm glad to see that setjmp() and longjmp() are still allowed. I'm just kidding by the way. For those C programmers who haven't encountered these before, it is a powerful way to do a "goto" in C. Powerful in the sense that you can jump anywhere, not limited to the same function. If it's used at all these days, it's used for exception handling. More info: https://en.wikipedia.org/wiki/Setjmp.h

These are used /everywhere/ in PostgreSQL, exactly for exception handling. The result isn't bad at all, but indeed, too powerful a tool for 99% of developers

Re: Banned C standard library functions in Git source code

#57

Post by saagarjha »

susam wrote: post #52
saagarjha wrote: post #35

Earlier quoted context omitted.

I see zero use of those in the codebase, so perhaps they should be banned too. Or maybe they’re not on this list because nobody was using them already?

I have worked in large code bases (RSA NetWitness, Oracle Database, etc.) where setjmp/longjmp were used to create macros for exception handling using TRY-CATCH-ENDTRY blocks in C.

Personally, I feel like wrapping exception handlers in macros makes it easy for people to do unsafe things with it like dynamically allocating memory or calling system functions that can’t handle it correctly.

Re: Banned C standard library functions in Git source code

#58

Post by asveikau »

slovenlyrobot wrote: post #8

That's a surprisingly small list, missing e.g. sscanf / gets / strtok / all the other "usual suspects" at least

I don't see a huge problem with strtok as long as it isn't a multi threaded program. It is not in gets territory which is literally impossible to use correctly.

Re: Banned C standard library functions in Git source code

#59

Post by ryandrake »

alister wrote: post #26

I'm glad to see that setjmp() and longjmp() are still allowed. I'm just kidding by the way. For those C programmers who haven't encountered these before, it is a powerful way to do a "goto" in C. Powerful in the sense that you can jump anywhere, not limited to the same function. If it's used at all these days, it's used for exception handling. More info: https://en.wikipedia.org/wiki/Setjmp.h

I think reasonable people can debate this one. setjmp()/longjmp() are very useful when working with libpng [1] and jpeglib [2], as you mentioned, as a crude exception handling mechanism. I have seen these functions used in production safely for that purpose. I can imagine other horrible uses for them though. Unlike things like strcpy() which are security-holes-by-design, setjmp()/longjmp() should be in a "carefully code review the exact way these are used" list rather than a banned list.

1: http://www.libpng.org/pub/png/libpng.html 2: https://www.ijg.org

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