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* [PATCH] system_data_types.7: void *: Add info about generic function parameters and return value
@ 2020-10-02  9:43 Alejandro Colomar
  0 siblings, 0 replies; only message in thread
From: Alejandro Colomar @ 2020-10-02  9:43 UTC (permalink / raw)
  To: mtk.manpages, eggert, David.Laight
  Cc: Alejandro Colomar, linux-man, gcc-patches, libc-alpha, linux-kernel

Reported-by: Paul Eggert <>
Reported-by: David Laight <David.Laight@ACULAB.COM>
Signed-off-by: Alejandro Colomar <>

Paul and David,
Thanks for your input!


 man7/system_data_types.7 | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/man7/system_data_types.7 b/man7/system_data_types.7
index aab64e002..6451782db 100644
--- a/man7/system_data_types.7
+++ b/man7/system_data_types.7
@@ -1903,6 +1903,16 @@ and back.
 Conversions from and to any other pointer type are done implicitly,
 not requiring casts at all.
+Note that this feature prevents any kind of type checking:
+the programmer should be careful not to cast a
+.I void *
+value to a type incompatible to that of the underlying data,
+because that would result in undefined behavior.
+This type is useful in function parameters and return value
+to allow passing values of any type.
+The function will usually use some mechanism to know
+of which type the underlying data passed to the function really is.
 A value of this type can't be dereferenced,
 as it would give a value of type
@@ -1926,6 +1936,12 @@ values.
 Conforming to:
 C99 and later; POSIX.1-2001 and later.
+See also:
+.BR malloc (3),
+.BR memcmp (3),
+.BR memcpy (3),
+.BR memset (3)
 See also the
 .I intptr_t

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2020-10-02  9:43 [PATCH] system_data_types.7: void *: Add info about generic function parameters and return value Alejandro Colomar

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