COMP: Forward-declare itk::Indent in itkPrintHelper.h#6252
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itkPrintHelper.h is included from itkMacro.h. Common ITK headers include
itkIndent.h, which itself includes itkMacro.h, which transitively includes
itkPrintHelper.h. When itkIndent.h is the include-chain entry point, the
recursive inclusion of itkIndent.h from itkPrintHelper.h's prologue is a
header-guard no-op — class itk::Indent has NOT yet been declared at the
point itkPrintHelper.h is parsed.
Most toolchains tolerate this because the only reference to Indent in
this file is a function parameter declaration (`const Indent & indent`),
and many parsers accept forward use of an undeclared type at parse time.
Stricter configurations (Apple Clang dbg, AppleClang ASanUBSan, ClangMain,
TSan, gcc 11.4 TBB-Debug, MSVC 2022 Static-DebugTBB, Valgrind, Coverage)
reject it as:
itkPrintHelper.h:97:44: error: unknown type name 'Indent'
The fix is the same pattern already used a few lines above for NumericTraits:
add an explicit forward declaration of class Indent inside namespace itk
before the namespace itk::print_helper block. Every PrintNumericTrait()
call site already #includes itkIndent.h directly or transitively (they
need to stream `os << indent`), so the forward declaration is sufficient
for the template's parameter list to parse; the full Indent definition is
visible at every instantiation site.
Symptom across 8+ Nightly / Expected Nightly platforms (2026-05-11):
CE=1 / TF=0 / TN=~2660 — one compile error in ITKCommon blocks the
entire test grid.
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May 12, 2026
dzenanz
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Fix the common-mode compile error in
itkPrintHelper.hthat breaks 8+ Nightly / Expected Nightly platforms (Mac11/12/13/14/15/26.x, Windows VS2022 Debug, Ubuntu gcc11 TBB-Debug, Valgrind, Coverage) with the same shapeCE=1 / TF=0 / TN=~2660— one compile error inITKCommonblocks the entire test grid.Root cause
itkPrintHelper.h:97uses an unqualifiedIndentin a parameter declaration:itkPrintHelper.his included fromitkMacro.h, which is itself included fromitkIndent.h. WhenitkIndent.his the include-chain entry point (the common case for any header that streams anIndent), the recursive inclusion ofitkIndent.hfromitkPrintHelper.h's prologue is a header-guard no-op —class itk::Indenthas not yet been declared whenitkPrintHelper.h's body is parsed.Stricter toolchain configurations reject this:
Local builds against ITK's pixi-managed Clang tolerate it; the failures only surface on Apple Clang dbg / ASanUBSan / TSan / ClangMain, MSVC 2022 Static-Debug, gcc 11.4 TBB-Debug, valgrind, and coverage builds.
Fix
Mirror the existing
NumericTraitsforward declaration a few lines above, addingclass Indent;inside thenamespace itk { ... }block. EveryPrintNumericTrait()call site already#includesitkIndent.hdirectly or transitively (they need the full definition to streamos << indent), so the forward declaration is sufficient for parameter-list parsing and the template instantiates against the full definition at every call site.Affected builds on the 2026-05-11 dashboard