table of content file is empty after pdflatex compilation

Question

On compiling a tex file into a pdf by pdflatex sample.tex, which contains \tableofcontents command, file sample.toc is generated as expected. However it is empty (0 bytes).

Here are the files:

sample.tex

\documentclass[12pt]{article}
\usepackage[utf8]{inputenc}
\usepackage{amsmath}
\begin{document}
\tableofcontents
\section{First Section}
some math here
\begin{align} 
&n + \sum_{i=1}^{\lfloor \lg n \rfloor} 2^i \
&= n + \frac{2(1-2^{\lfloor \lg n \rfloor})}{1-2}
\end{align*}
\section*{second section}
plain text here
\end{document}

sample.toc

sample.aux

\relax 
\gdef \@abspage@last{1}

sample.log

This is pdfTeX, Version 3.141592653-2.6-1.40.24 (TeX Live 2022/Arch Linux) (preloaded format=pdflatex 2022.5.18)  18 MAY 2022 15:33
entering extended mode
 restricted \write18 enabled.
 %&-line parsing enabled.
**sample.tex
(./sample.tex
LaTeX2e <2021-11-15> patch level 1
L3 programming layer <2022-04-10>
(/usr/share/texmf-dist/tex/latex/base/article.cls
Document Class: article 2021/10/04 v1.4n Standard LaTeX document class
(/usr/share/texmf-dist/tex/latex/base/size12.clo
File: size12.clo 2021/10/04 v1.4n Standard LaTeX file (size option)
)
\c@part=\count185
\c@section=\count186
\c@subsection=\count187
\c@subsubsection=\count188
\c@paragraph=\count189
\c@subparagraph=\count190
\c@figure=\count191
\c@table=\count192
\abovecaptionskip=\skip47
\belowcaptionskip=\skip48
\bibindent=\dimen138
)
(/usr/share/texmf-dist/tex/latex/base/inputenc.sty
Package: inputenc 2021/02/14 v1.3d Input encoding file
\inpenc@prehook=\toks16
\inpenc@posthook=\toks17
)
(/usr/share/texmf-dist/tex/latex/amsmath/amsmath.sty
Package: amsmath 2021/10/15 v2.17l AMS math features
\@mathmargin=\skip49
For additional information on amsmath, use the `?' option.
(/usr/share/texmf-dist/tex/latex/amsmath/amstext.sty
Package: amstext 2021/08/26 v2.01 AMS text
(/usr/share/texmf-dist/tex/latex/amsmath/amsgen.sty
File: amsgen.sty 1999/11/30 v2.0 generic functions
@emptytoks=\toks18
\ex@=\dimen139
))
(/usr/share/texmf-dist/tex/latex/amsmath/amsbsy.sty
Package: amsbsy 1999/11/29 v1.2d Bold Symbols
\pmbraise@=\dimen140
)
(/usr/share/texmf-dist/tex/latex/amsmath/amsopn.sty
Package: amsopn 2021/08/26 v2.02 operator names
)
\inf@bad=\count193
LaTeX Info: Redefining \frac on input line 234.
\uproot@=\count194
\leftroot@=\count195
LaTeX Info: Redefining \overline on input line 399.
\classnum@=\count196
\DOTSCASE@=\count197
LaTeX Info: Redefining \ldots on input line 496.
LaTeX Info: Redefining \dots on input line 499.
LaTeX Info: Redefining \cdots on input line 620.
\Mathstrutbox@=\box50
\strutbox@=\box51
\big@size=\dimen141
LaTeX Font Info:    Redeclaring font encoding OML on input line 743.
LaTeX Font Info:    Redeclaring font encoding OMS on input line 744.
\macc@depth=\count198
\c@MaxMatrixCols=\count199
\dotsspace@=\muskip16
\c@parentequation=\count266
\dspbrk@lvl=\count267
\tag@help=\toks19
\row@=\count268
\column@=\count269
\maxfields@=\count270
\andhelp@=\toks20
\eqnshift@=\dimen142
\alignsep@=\dimen143
\tagshift@=\dimen144
\tagwidth@=\dimen145
\totwidth@=\dimen146
\lineht@=\dimen147
@envbody=\toks21
\multlinegap=\skip50
\multlinetaggap=\skip51
\mathdisplay@stack=\toks22
LaTeX Info: Redefining [ on input line 2938.
LaTeX Info: Redefining ] on input line 2939.
)
(/usr/share/texmf-dist/tex/latex/l3backend/l3backend-pdftex.def
File: l3backend-pdftex.def 2022-04-14 L3 backend support: PDF output (pdfTeX)
\l__color_backend_stack_int=\count271
\l__pdf_internal_box=\box52
) (./sample.aux)
\openout1 = `sample.aux'.
LaTeX Font Info:    Checking defaults for OML/cmm/m/it on input line 5.
LaTeX Font Info:    ... okay on input line 5.
LaTeX Font Info:    Checking defaults for OMS/cmsy/m/n on input line 5.
LaTeX Font Info:    ... okay on input line 5.
LaTeX Font Info:    Checking defaults for OT1/cmr/m/n on input line 5.
LaTeX Font Info:    ... okay on input line 5.
LaTeX Font Info:    Checking defaults for T1/cmr/m/n on input line 5.
LaTeX Font Info:    ... okay on input line 5.
LaTeX Font Info:    Checking defaults for TS1/cmr/m/n on input line 5.
LaTeX Font Info:    ... okay on input line 5.
LaTeX Font Info:    Checking defaults for OMX/cmex/m/n on input line 5.
LaTeX Font Info:    ... okay on input line 5.
LaTeX Font Info:    Checking defaults for U/cmr/m/n on input line 5.
LaTeX Font Info:    ... okay on input line 5.
(./sample.toc)
\tf@toc=\write3
\openout3 = `sample.toc'.
[1
{/var/lib/texmf/fonts/map/pdftex/updmap/pdftex.map}]
(./sample.aux) ) 
Here is how much of TeX's memory you used:
 1183 strings out of 478238
 18440 string characters out of 5850456
 311201 words of memory out of 5000000
 19469 multiletter control sequences out of 15000+600000
 473275 words of font info for 42 fonts, out of 8000000 for 9000
 1141 hyphenation exceptions out of 8191
 54i,10n,62p,202b,121s stack positions out of 5000i,500n,10000p,200000b,80000s
</usr/share/texmf-dist/fonts/type1/public/amsfonts/cm/cmbx12.pf
b></usr/share/texmf-dist/fonts/type1/public/amsfonts/cm/cmex10.pfb></usr/share/
texmf-dist/fonts/type1/public/amsfonts/cm/cmmi12.pfb></usr/share/texmf-dist/fon
ts/type1/public/amsfonts/cm/cmmi8.pfb></usr/share/texmf-dist/fonts/type1/public
/amsfonts/cm/cmr12.pfb></usr/share/texmf-dist/fonts/type1/public/amsfonts/cm/cm
r8.pfb></usr/share/texmf-dist/fonts/type1/public/amsfonts/cm/cmsy10.pfb></usr/s
hare/texmf-dist/fonts/type1/public/amsfonts/cm/cmsy8.pfb>
Output written on sample.pdf (1 page, 71619 bytes).
PDF statistics:
 48 PDF objects out of 1000 (max. 8388607)
 28 compressed objects within 1 object stream
 0 named destinations out of 1000 (max. 500000)
 1 words of extra memory for PDF output out of 10000 (max. 10000000)

How can I fix, so sample.toc is correctly generated, and hence render table of contents in the pdf file by a second compilation of pdflatex sample.tex?

Answer 1

The \section* command is, in fact, for sections that won't appear in the table of content. Replace them with \section and it'll work.

Just removing the two spurrious starts gives the output below.