[libc-commits] [PATCH] D143782: [libc] Prevent printf index mode crashes

[Michael Jones via Phabricator via libc-commits]

michaelrj created this revision.
michaelrj added reviewers: sivachandra, lntue.
Herald added subscribers: libc-commits, ecnelises, tschuett, arphaman.
Herald added projects: libc-project, All.
michaelrj requested review of this revision.

The posix standard defines an alternate mode for printf where the
conversions also have an index that describes which argument to select.
Due to how variadic arguments work in C, to reach the nth argument all
n-1 previous arguments must be read with their correct types. If the
format string does not specify the types for a continuous set of
arguments, then the arguments after the discontinuity cannot be safely
read. This patch causes all conversions requesting an argument that
comes after a gap be treated as raw (i.e. the conversion string is
printed literally).


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D143782

Files:
  libc/src/stdio/printf_core/core_structs.h
  libc/src/stdio/printf_core/parser.cpp
  libc/src/stdio/printf_core/parser.h
  libc/test/src/stdio/printf_core/parser_test.cpp

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