Debugging

This part of the wiki collects all the information related to debugging GHC: that includes debugging the compiler itself, the libraries, the runtime system, the code generator, or the build system.

• Testing and measuring
  • Use the testsuite to test the compiler on thousands of regression tests
  • Use the nofib suite, and the nofib-analyse tool, to compare performance on 50-odd benchmarks.
  • Use count_lines to count the number of lines of code in the compiler
  • Use compareSizes to compare the sizes of corresponding .o or .hi files in two trees.

• Reproducing the test case. You may need to install some packages to reproduce the test case, and that may take a little care: Debugging/InstallingPackagesInplace.

• Debugging the compiler itself. If you're debugging a compiler panic or some problem in GHC itself, then go to Debugging/Compiler

• Debugging a compiled program. If the compiled program crashes or panics, then go to Debugging/CompiledCode

• Debugging the runtime system. See Debugging/RuntimeSystem

• Performance debugging.
  • Debugging/ProfilingGhc: Profiling the compiler itself.
  • Debugging/TickyTicky: for debugging performance-related issues in compiled code. Typically for performance debugging of the Simplifier and Core-level optimisations.
  • Debugging/LowLevelProfiling: way to investigate low-level performance, typically for performance debugging of the code generator or RTS.

• Build failures. If you're trying to debug a build failure, then you probably want to look at
  • Building/Troubleshooting: Fixing common problems in a GHC build
  • Building/Modifying#Debugging: Debugging the build system

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count_lines

The count_lines script, which is put in $(TOP)/inplace/bin, counts source lines and comments. The command-line arguments are the Haskell source files to count.

bash-3.2$ $head/count_lines compiler/*/*hs

                      Code  Comments
compiler/basicTypes    4565   5092
compiler/cmm           9685   4703
...
compiler/utils         6316   4669
compiler/vectorise     2608    669

TOTAL:               105893  86247

                      Code  Comments
Annotations.lhs          57     44
AsmCodeGen.lhs          591    333
Bag.lhs                 140     51
....
ZipCfgExtras.hs          43     33
ZipDataflow.hs          779    271

TOTAL:               105893  86247

The source for count_lines is in $(TOP)/utils/count_lines.

compareSizes

The compareSizes program compares the sizes of corresponding files in two trees:

$ ./compareSizes --hi ~/ghc/darcs/ghc ~/ghc/6.12-branch/ghc
        Size | Change | Filename
      25644 | -0.99% | compiler/stage1/build/Demand.hi
      21103 | -0.98% | compiler/stage2/build/Demand.hi
     180044 | -0.98% | libraries/base/dist-install/build/GHC/Classes.hi
       6415 | -0.58% | .../Data/Array/Parallel/Prelude/Base/Tuple.hi
       6507 | -0.57% | .../Data/Array/Parallel/Prelude/Base/Tuple.hi
   [...]
       3264 |  3.16% | .../Parallel/Unlifted/Sequential/Flat/Enum.hi
      51389 |  3.30% | .../build/Language/Haskell/Extension.hi
       1415 | 72.18% | libraries/base/dist-install/build/Data/Tuple.hi
   28752162 | -0.00% | TOTAL

Flags:

• --o to compare object files.
• --hi to compare interface files [DEFAULT]

There's a hack to avoid descending into '*_split' directories.

The source for compareSizes is in $(TOP)/utils/compare_sizes.