[llvm-bugs] [Bug 48363] New: clang-format using over 5GB of RAM on a C file with many arrays

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=48363

            Bug ID: 48363
           Summary: clang-format using over 5GB of RAM on a C file with
                    many arrays
           Product: clang
           Version: unspecified
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Formatter
          Assignee: unassignedclangbugs at nondot.org
          Reporter: tmatth at videolan.org
                CC: djasper at google.com, klimek at google.com,
                    llvm-bugs at lists.llvm.org

Created attachment 24228
  --> https://bugs.llvm.org/attachment.cgi?id=24228&action=edit
Problematic source file

I noticed that clang-format was running out of memory on a system with only
3.75GB available. It turns out that for a specific file
(https://aomedia.googlesource.com/aom/+/c15883a29b9dc3c28caa03e22b7368ed8355d834/av1/common/quant_common.c)
it is using over 5GB when invoked as follows:

/usr/bin/time -v clang-format -i --style=file aom/av1/common/quant_common.c
        Command being timed: "clang-format -i --style=file
aom/av1/common/quant_common.c"
        User time (seconds): 17.59
        System time (seconds): 1.49
        Percent of CPU this job got: 99%
        Elapsed (wall clock) time (h:mm:ss or m:ss): 0:19.14
        Average shared text size (kbytes): 0
        Average unshared data size (kbytes): 0
        Average stack size (kbytes): 0
        Average total size (kbytes): 0
        Maximum resident set size (kbytes): 5479164        <----------------
        Average resident set size (kbytes): 0
        Major (requiring I/O) page faults: 0
        Minor (reclaiming a frame) page faults: 1375531
        Voluntary context switches: 2
        Involuntary context switches: 136
        Swaps: 0
        File system inputs: 0
        File system outputs: 0
        Socket messages sent: 0
        Socket messages received: 0
        Signals delivered: 0
        Page size (bytes): 4096
        Exit status: 0


The file in question is 12875 lines, and does contain a number of arrays, but
this still seems like it shouldn't be quite so memory intensive. I've seen the
same behavior with both clang 10 and 12.

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