[clang-format] SkipMacroDefinitionBody breaks AlignConsecutiveMacros

[LekKit]

When enabling SkipMacroDefinitionBody, simple value definitions no longer get formatted properly via AlignConsecutiveMacros.

While it might be nontrivial, it might be a good idea to align indentation of macros that would be otherwise properly handled with AlignConsecutiveMacros, without actually formatting them. Or at least document that SkipMacroDefinitionBody and AlignConsecutiveMacros are mutually exclusive.

[llvmbot]

@llvm/issue-subscribers-clang-format

Author: LekKit (LekKit)

When enabling `SkipMacroDefinitionBody`, simple value definitions no longer get formatted properly via `AlignConsecutiveMacros`.

While it might be nontrivial, it might be a good idea to align indentation of macros that would be otherwise properly handled with AlignConsecutiveMacros, without actually formatting them. Or at least document that SkipMacroDefinitionBody and AlignConsecutiveMacros are mutually exclusive.

[owenca]

Please provide a reproducer with what's expected. By definition, SkipMacroDefinitionBody doesn't format the macro body including alignments.

[LekKit]

Consider following code (Taken from a real world codebase)

It includes multi-line function-like macros (Which I do not wish to be formatted in any way), and simple value definitions (Which I want to align nicely in a table-like pattern).

/*
 * Internal helper macros from RVVM (src/compiler.h)
 */

// BREAKABLE_SCOPE () {}
#undef BREAKABLE_SCOPE
#define BREAKABLE_SCOPE(name)                                                                                          \
    for (int MACRO_IDENT_NAME(breakable_scope_iter, name) = 1;                                                         \
        MACRO_IDENT_NAME(breakable_scope_iter, name);                                                                  \
        MACRO_IDENT_NAME(breakable_scope_iter, name) = 0)

// SCOPED_COND_NAMED (true, spin_lock(&lock), spin_unlock(&lock), ) {}
#undef SCOPED_COND_NAMED
#define SCOPED_COND_NAMED(cond, expr_pre, expr_post, name)                                                             \
    for (int MACRO_IDENT_NAME(scoped_cond_iter, name) = 1,                                                             \
        MACRO_IDENT_NAME(scoped_cond, name) = !!(cond) && (expr_pre, 1);                                               \
        MACRO_IDENT_NAME(scoped_cond_iter, name);                                                                      \
        MACRO_IDENT_NAME(scoped_cond_iter, name) = MACRO_IDENT_NAME(scoped_cond, name) && (expr_post, 0))              \
        BREAKABLE_SCOPE(name) if (MACRO_IDENT_NAME(scoped_cond, name))

// Portably cast to a non-constant pointer without triggering -Wconst-qual. Use with care!
#undef NONCONST_CAST
#if defined(GNU_EXTS)
#define NONCONST_CAST(type, x) ((type)((union { const void* _constptr; void* _ptr; }){ ._constptr = (const void*)(x), })._ptr)
#else
#define NONCONST_CAST(type, x) ((type)(void*)(x))
#endif

/*
 * NVMe spec definitions from RVVM (src/devices/nvme.c)
 */

// Controller Registers
#define NVME_REG_CAP1  0x00 // Controller Capabilities
#define NVME_REG_CAP2 0x04
#define NVME_REG_VS 0x08 // Version
#define NVME_REG_INTMS 0x0C // Interrupt Mask Set
#define NVME_REG_INTMC 0x10 // Interrupt Mask Clear
#define NVME_REG_CC 0x14 // Controller Configuration
#define NVME_REG_CSTS 0x1C // Controller Status
#define NVME_REG_AQA 0x24 // Admin Queue Attributes
#define NVME_REG_ASQ1 0x28 // Admin Submission Queue Base Address
#define NVME_REG_ASQ2 0x2C
#define NVME_REG_ACQ1 0x30 // Admin Completion Queue Base Address
#define NVME_REG_ACQ2 0x34

When I set the following in the config, I would expect that it would do exactly what I want. Instead it actually does nothing at all - apparently SkipMacroDefinitionBody disables AlignConsecutiveMacros altogether.

# Do not format macro bodies
SkipMacroDefinitionBody: true

# Pretty table-like alignment for definitions
AlignConsecutiveMacros: AcrossEmptyLinesAndComments

If I then disable SkipMacroDefinitionBody in the above config, clang-format messes up my multi-line macro bodies, which I don't like, but at least the value definitions are aligned quite nicely.

/*
 * Internal helper macros from RVVM (src/compiler.h)
 */

// BREAKABLE_SCOPE () {}
#undef BREAKABLE_SCOPE
#define BREAKABLE_SCOPE(name)                                                                                          \
  for (int MACRO_IDENT_NAME(breakable_scope_iter, name) = 1; MACRO_IDENT_NAME(breakable_scope_iter, name);             \
       MACRO_IDENT_NAME(breakable_scope_iter, name) = 0)

// SCOPED_COND_NAMED (true, spin_lock(&lock), spin_unlock(&lock), ) {}
#undef SCOPED_COND_NAMED
#define SCOPED_COND_NAMED(cond, expr_pre, expr_post, name)                                                             \
  for (int MACRO_IDENT_NAME(scoped_cond_iter, name) = 1,                                                               \
                                              MACRO_IDENT_NAME(scoped_cond, name) = !!(cond) && (expr_pre, 1);         \
       MACRO_IDENT_NAME(scoped_cond_iter, name);                                                                       \
       MACRO_IDENT_NAME(scoped_cond_iter, name) = MACRO_IDENT_NAME(scoped_cond, name) && (expr_post, 0))               \
  BREAKABLE_SCOPE(name) if (MACRO_IDENT_NAME(scoped_cond, name))

// Portably cast to a non-constant pointer without triggering -Wconst-qual. Use with care!
#undef NONCONST_CAST
#if defined(GNU_EXTS)
#define NONCONST_CAST(type, x)                                                                                         \
  ((type)((union {                                                                                                     \
     const void *_constptr;                                                                                            \
     void *_ptr;                                                                                                       \
   }){                                                                                                                 \
              ._constptr = (const void *)(x),                                                                          \
          })                                                                                                           \
       ._ptr)
#else
#define NONCONST_CAST(type, x) ((type)(void *)(x))
#endif

/*
 * NVMe spec definitions from RVVM (src/devices/nvme.c)
 */

// Controller Registers
#define NVME_REG_CAP1  0x00 // Controller Capabilities
#define NVME_REG_CAP2  0x04
#define NVME_REG_VS    0x08 // Version
#define NVME_REG_INTMS 0x0C // Interrupt Mask Set
#define NVME_REG_INTMC 0x10 // Interrupt Mask Clear
#define NVME_REG_CC    0x14 // Controller Configuration
#define NVME_REG_CSTS  0x1C // Controller Status
#define NVME_REG_AQA   0x24 // Admin Queue Attributes
#define NVME_REG_ASQ1  0x28 // Admin Submission Queue Base Address
#define NVME_REG_ASQ2  0x2C
#define NVME_REG_ACQ1  0x30 // Admin Completion Queue Base Address
#define NVME_REG_ACQ2  0x34