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authorZack Weinberg <zackw@panix.com>2018-02-05 14:42:29 -0500
committerZack Weinberg <zackw@panix.com>2018-02-05 19:59:03 -0500
commit26c07172cde74617ca7214c93cdcfa75321e6b2b (patch)
tree27828020addf2f8ee8b44801169428b1e149f38f /NEWS
parentde6da571eeff41e69a28744b4c57e219828e26bc (diff)
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Remove getc and putc macros from the public stdio.h.
The getc and putc macros in the public stdio.h expand to call _IO_getc and _IO_putc respectively. As _IO_getc, fgetc, and getc are all aliases for the same function, and _IO_putc, fputc, and putc are also all aliases for the same function, the macros are pointless. The C standard does not require getc and putc to be macros, so let's just not have macros. All four symbols are exported from libc.so at the same, ancient symbol version, so there should be no risks for binary compatibility. Similarly, the getchar and putchar inlines in bits/stdio.h forward to getc and putc instead of their _IO_ aliases. As a change from longstanding historical practice, this does seem like it might break _something_, so there is a note in NEWS, which is also a convenient place to advise people that if they thought getc and putc had reduced per-character overhead they should consider using getc_unlocked and putc_unlocked instead. (These are also not macros, but when optimizing, they are inlines.) * libio/stdio.h: Don't define getc or putc as macros. * libio/bits/stdio.h (getchar, putchar): Use getc and putc, not _IO_getc and _IO_putc.
Diffstat (limited to 'NEWS')
-rw-r--r--NEWS7
1 files changed, 6 insertions, 1 deletions
diff --git a/NEWS b/NEWS
index 3ac57ec..06ae43d 100644
--- a/NEWS
+++ b/NEWS
@@ -13,7 +13,12 @@ Major new features:
Deprecated and removed features, and other changes affecting compatibility:
- [Add deprecations, removals and changes affecting compatibility here]
+ * The stdio.h functions 'getc' and 'putc' are no longer defined as macros.
+ This was never required by the C standard, and the macros just expanded
+ to call alternative names for the same functions. If you hoped getc and
+ putc would provide performance improvements over fgetc and fputc, instead
+ investigate using (f)getc_unlocked and (f)putc_unlocked, and, if
+ necessary, flockfile and funlockfile.
Changes to build and runtime requirements: